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I
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The Walschaert
Locomotive Valve Gear
A PRACTICAL TREATISE ON THE LOCOMOTIVE VALVE
Actuating Mechanism Originally
Invented by Egide Walschaerts
With the History of Its Development by American and Euro-
pean Engine Designers, and Its Evolution into the
Mechanically Correct Locomotive Valve
Gear of the Present Day.
IN FOUR GENERAL DIVISIONS, EMBRACING:
Analysis of the Motion. — Designing and Erecting the Gear. —
Proof of the Superiority of the Walschaert Gear in
Locomotive Service. — Catechal Questions
and Answers for Instruction and
Examination.
Intended for the Engineer or Mechanic Who Wishes to Extend
His Knowledge of Locomotive Valve Gears to the Type
That is Rapidly Superseding the Stephenson
Eccentric Motion of the Past Century.
w. w.
BY
WOOD
/
Air Brake Inspector
Fully Illustrated with Ideal Sketches and Instruction Models, Line
Engravings of Side Elevations and Plans of the Gear in Its
Different Phases; Engravings of Locomotives of All '
Branches of Service Using the Walschaert Gear.
Diagrams to Illustrate the General Text and Formulas ; Large
Folding Plates and Diagrams of Different Types of the
Walschaert Motion with Movable, Card-
^^ 7" board Working Models of the Valves.
•*i-f*
-u
y NEW YORK
THE NiumAN W. HENLEY PUBLISHING CO.
132 Nassau Street
1907
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'^'■•'Cl
IRAU
Copyright, 1906,
BY
THE NORMAN W. HENLEY PUBLISHING CO.
Composition, Printing and Electrotyping by
Publishers Printing Company, New York, U. S. A.
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CONTENTS
FIRST DIVISION
PAGE
Analysis of the Walschaert Valve Gear ... 11-92
SECOND DIVISION
Designing and Erecting the Walschaert
Valve Gear 95-1 26
THIRD DIVISION
Advantages of the Walschaert Valve Gear . . 1 29-1 48
FOURTH DIVISION
Questions and Answers Relating to the
Walschaert Valve Gear 151-185
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PREFACE
In the capacity of an air-brake instructor, it has
been the pleasure of the author of this book to endeavor
to impart information on other mechanical and general
railway subjects, as well as those relating to his special
profession, to the railroad men with whom business
has brought him in contact, and since the tendency
of locomotive builders has been toward the intro-
duction of the style of valve gear that was invented
by Egide Wakchaert many years ago, and never
taken up in this country through sheer conservatism
until the force of combined circumstances compelled
its adoption, the many requests for information con-
cerning that special device have revealed the fact
that while there are legion of books devoted almost
wholly to the so-called Stephenson Unk motion, there
was not one book in existence given wholly to the
subject of the Walschaert valve gear, and nothing in
print that explained that style of motion to the satis-
faction of the locomotive engineer, the shop man, and
the master mechanic, alike; in fact, no treatise could
be found that extended further than an elementary
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6 PREFACE
description of the gear, and this book is the result of
a determination to supply the deficiency.
The American Locomotive Company, and the
Baldwin Locomotive Works, have issued from time
to time pamphlets illustrating and giving the general
dimensions of their recently constructed engines, and
they have very kindly permitted the use of many of
those plates for the purpose of illustrating the text of
this work.
In that portion relating to the laying-out of the
Walschaert gear for any particular engine, from the
designer's or the shop-man's point of view, I have
quoted and borrowed several illustrations from the
very able paper read at the 1906 convention of the
American Railway Master Mechanics' Association, by
Mr. C. J. Mellin, Designing Engineer of the American
Locomotive Company. This paper was written on
the subject of Special Valve Gears other than the
Stephenson link motion, and contained in a condensed
form an exposition of the Walschaert principle of
valve actuation modified by the requirements of present-
day railway practice and the improvements suggested
by progressive American locomotive builders. The
Baldwin Locomotive Works were of great assistance to
the author in furnishing twin diagrams of the Wal-
schaert gear in connection with valves of outside ad-
mission and inside admission that would undoubtedly
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PREFACE 7
be the chief and most interesting features of any
treatise on this type of valve motion that could be
written, and' are reproduced directly from the models
used in designing the valve gear at the greatest loco-
motive works in the world.
It would be natural to presume that the reader of
this book, with interest enough in the Walschaert gear
to prompt him to make an effort to secure information
in regard to that style of valve motion, would already
be possessed of at least a fair working knowledge of
the principles of the common valve itself; therefore,
the valve is herein treated superficially, except in its
actions that may be peculiarly induced by the motion,
of the Walschaert gear.
The Author,
November, 1906.
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FIRST DIVISION
Analysis of the waISchaert
valve gear
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THE WALSCHAERT VALVE GEAR
FIRST DIVISION
ANALYSIS OF THE WALSCHAERT VALVE
GEAR
From the time of the building of the first locomotive
engine, the methods employed to actuate the valve
that is required to supply steam from the boiler to the
cylinder, and discharge it therefrom after it has per-
formed its work, were experimental and crude, until
along about the year 1840 the double-eccentric hook-
motion had naturally evolved into the shifting link
action, under the name it has ever since borne — ^the
Stephenson link motion; and in spite of our general
lack of conservatism, that gear is, to-day, the vital
part of practically all American locomotives, although
our engines have increased in weight during recent
years to such an extent that the necessary enlargement
of the parts of the valve motion has given them a
tonnage to be started and stopped twice in every
revolution of the driving wheels that should have
prohibited the use of such heavy reciprocating part§
before jiow.
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12 THE WALSCHAERT VALVE GEAR
For this and other reasons, our locomotive build-
ers have been casting about for some time in search of
a valve gear more suited to modem condition^, with
the result that many railroads have recently received
new engines equipped with what is known as the
Walschaert valve gear, a motion that was originated
almost as long ago as the Stephenson link, and that
has been in continuous and highly satisfactory use
on European railways ever since; given desultory
trials in America at intervals in the latter part of the
last century by those prejudiced toward it, and dropped
from sight, it has risen into our view again through
a sheer necessity, and there is a general desire, now,
to get acquainted with the principle of its operation.
About the year 1844 — ^the transition period in the
development of valve motions from the undecided to
the accepted principles — Mr. Egide Walschaerts (the
final s in his name has been dropped in its application
to that type of valve gear), who was acting at that time
as Master Mechanic of the Belgian State Railways,
seems to have been dissatisfied with the results obtained
from the use of two eccentrics in governing the motion
of one main valve, and most likely foreseeing the pos-
sibilities in the line of economy by using the expansive
power of the steam in the cylinders — something that
had always been impossible of attainment with the
hook motion — ^he invented the form of valve gear that
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THE WALSCHAERT VALVE GEAR 13
•
bears his name, and to-day it is uncommon to see a
picture of a locomotive belonging to any railway of
any country in Europe, that is not equipped with the
Walschaert gear, — monuments of power, they are,
proclaiming the genius of the inventor of that most
vital part of the locomotive. Europeans have made the
most of this device and have brought out its best
points, and it is worth while to note that in practically
every case their engines use the D-slide valve — or, at
least, outside admission valves — in connection with
the Walschaert gear: There's a reason.
Bom in the little village of Mechlin, near Brussels,
in 1820, Walschaert was but fifteen years old when
the State Railway lines were extended to Malines,
where the main shops were located; but railway
mechanics appealed strongly to the young man, and
it is known that he was employed in the State Railway
shops in 1842, and that two years later, as locomotive
foreman, he had gained an enviable reputation as a
successful railway mechanical engineer. It was not
Icmg until he was appointed chief superintendent of
the shops, and having gained this advancement at a
bound, being still a young man and a master at his
craft, it is a fact that has never been explained that
Egide Walschaert remained at just this level in his
profession for the rest of his life.
Neither did he patent his own device. It seems
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14 THE WALSCHAERT VALVE GEAR
that the State Railways would not permit a foreman —
as he was in 1844-^ to make personal profit out of his
own invention; so, his friend, M. Fisher, an engineer
of the same company, made application in Walschaert's
name, on October of the above year, for a patent
relating to an improved valve gear, of which our
present-day Walschaert motion is a close duplicate.
The patent was allowed, and M. Fisher never claimed
any credit for himself. It was in 1848 that Walschaert
applied the gear to one of his engines and the results
were all that he had anticipated. His device attracted
attention throughout the Continent, and in due time
came into general use on the principal railways of
Europe. His engine equipped with the trial valve
gear was the first one on the State railways to have a
variable cut-oflF, for all of their other engines had the
old hook motion, and as Egide Walschaert had never
seen — possibly had never heard of — a shifting link,
the problem that he worked out was greater than we,
of to-day, can realize at first thought.
He was awarded a gold medal, and a diploma and
honorable mention for his improved valve gear at the
Exposition at Paris in 1878, and also at Antwerp
in 1883. His death occurred at Saint-Gilles, near
Brussels, on February i8th, 1901.
It has been said of the man whose mind conceived
this theory of valve-actuating mechanism, that ** Egide
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THE WALSCHAERT VALVE GEAR 15
Walschaert wrought better than he knew, for this gear
now seems indispensable to meet conditions recently
arisen because of the development of the locomotive
in this country, of which the inventor could not possibly
have dreamed. His work now meets a need which did
not exist during the lifetime of the mventor, and for
this reason he is entitled to credit for solving a problem
of, to him, a future generation."
It is purposed here to explain the theory and action
of Walschaert's valve gear, showing that his principle
was not only an improvement on the old hook motion,
but even at that early date was a better device than
the modem, and commonly used, Stephenson link
motion; to show it in as simple and plain a manner as
possible, going through the process of its evolution
from the common sawmill engine, that some of the
readers hereof may have tended, and we will build up
the Walschaert gear from it, ourselves, with the help
of a few drawings and photographic views.
In taking up the study, or entering into an analysis,
of any particular form of locomotive valve gear, it
must be assumed that the principle of the plain steam
engine in its most primitive form is already under-
stood — ^at least, the valve itself. We will, however,
start, in this building-up of our prospective Walschaert
motion, with the plainest pattern of valve-actuating
gear, and explain its actions so far as may be necessary
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i6 THE WALSCHAERT VALVE GEAR
before its further evolution begins. As to the valve, —
it is a study itself, separate from the subject of this
article, but must be gotten acquainted with before
starting into the subject of the mechanism that oper-
ates it; for, if the reader does not understand some-
what of the construction and functions of the valve,
this is a step ahead of him — ^but a step that may easily
be overtaken.
There are several different designs of steam valves,
but all do practically the same work: that of admitting
and releasing steam to and from the cylinder in which
the energy of the steam is transformed into piston
power — the power that makes the wheels go 'round.
With all of the common types of valve there are but
two ports to the cylinder — one to each end — and
while the valve is admitting live steam to the cylinder
through one of these ports, it is discharging the ex-
hausted steam from the other port, and vice versa.
Usually, the direct exhaust port is located midway
between the two steam admission ports. An outside
admission valve is one that starts the piston moving
in the same direction in which the valve is travelling
at the time the admission port is opened, and the
admission ports are opened outside of either end of
the valve while during the same time the other end of
the cylinder is discharging its exhausted steam through
the cavity in the centre of the valve. Such a valve
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THE WALSCHAERT VALVE GEAR 17
may be either of the round, ** piston" type, or the flat,
plane-faced D-slide pattern. An inside admission
valve does its work in exactly the reverse manner to
that of the one just described, and all inside admission
valves in conamon use are of the piston type, which in
construction are really two ordinary pistons with
metal packing rings, and with a tubular connection
from one piston to the other; this connecting cylinder
is usually made hollow in order that the pressure
against the outer ends of the pistons will be held in
perfect equalization and the valve be thereby more
uniformly balanced; in some cases, however, the
opening through this "spool," — as the whole valve,
complete, is termed, — ^is closed. It is claimed for the
piston valve, by its friends, that it is a perfectly balanced
valve — ^with an "open spool"; but while it is evenly
balanced "fore and aft," the frictional surfaces with
the steam pressure bearing against them — the packing
rings — are not balanced at all; while a D-slide valve
may have nearly all of its bearing surface balanced.
Lap is the distance by which* the valve overcovers the
steam admission port — the distance the valve must be
moved from an exact central position on its seat before
the port begins to open to admit steam to the cylinder.
Lead is the distance that the admission port is
specially opened at the time when the piston is at an
end — either end — of the cylinder, at the prime start — ^.
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i8 THE WALSCHAERT VALVE GEAR
or finish, both are the same — of its stroke. Lead is
given in order that steam may be admitted between
the piston and the cylinder head, toward the com-
pletion of the stroke, as a means of cushioning the
piston and thereby tempering the sudden reversion of
its motion; the same eflfect is, however, more econom-
ically produced by closing the exhaust from the cylinder
at an earlier period in the finish of the piston's stroke,
thus making use of the confined dead steam in its
CXHAU8T
Fig. I. — ^The Main Valve; showing admission and exhaust
ports, the cylinder and piston.
compressible resistance as a cushion; this earlier
closing is spoken of as the "cut-off'' of the exhaust.
Cut-off more commonly has reference to the closing
of the port for admission of live steam to'the cylinder
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THE WALSCHAERT VALVE GEAR 19
and the point in the travel of the valve at which the
ciit-off occurs is fixed by the position of the link in
the link-block, as will be explained later — ^when we
have taken up the action of the valve gear; this position
of the gear is, in turn, determined by the notch of the
quadrant in which the reverse lever is placed. Fig. i
is a simple sketch illustrating the theory of the main
valve of an engine.
But it doesn't make any difference what kind of a
valve is used in connection with the Walschaert gear
any. more than it does with the Stephenson link motion,
and the former may be substituted on any engine in
place of the latter gear without making any change
in the valve, or cylinders, or any part of the steam-
distributing mechanism. But, although either inside
admission or outside admission valves may be used
with the Walschaert gear, as the user may prefer, a
better all 'round design of this gear can be produced
when an outside admission valve is specified.
There is a difference, though, in "setting-up" the
Walschaert gear as between the valves of inside and
outside admission; a difference only in the position of
the eccentric in its relation to the main crank-pin, and
the connections, as they must be made, between the
radius rod and valve-stem, and the combination
lever; these points, however, will be explained at the
proper time.
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20 THE WALSCHAERT VALVE GEAR
Fig. 2 represents the idea of "direct motion" in
the valve-actuating mechanism, and is the simplest
form of the common steam engine, with fixed cut-offs
and non-reversible, and it will be the engine in the
Fig. 2. — ^The Simplest Form of Steam Engine; Direct
Valve Motion.
rough — the rough ashlar — that we are to develop, for,
while this engine will run, and do very well under
certain conditions, it is a wasteful power-producer
and is limited to the last degree in the work expected
of an engine: it can only turn its crank in one direction,
and uses approximately as much steam each time
that it turns that crank againct a light load as it does
when working against a heavier load. We are to
supply those deficiencies noted, and bring it up to
an equivalent of the engine that is on each side of a
modem locomotive.
With any engine, the port opening for admission of
steam to the cylinder must be one-fourth of the cycle
of motion ahead of the piston. Therefore, if the
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THE WALSCHAERT VALVE GEAR 21
connection from eccentric to valve is through a direct
line of motion, as shown, without any levers inter-
posed or "rocker-arms" to reverse the direction of
movement, then, with the main-pin in the position as
shown in Fig. 2, the eccentric must be located at £,
one-fourth of the wheel's circle, or 90 degrees, ahead
of the crank-pin — assuming the engine to be running
forward— to the right.
But before going further it is best to explain how to
take the expression, in hearing it said that an eccentric
is "ahead" or "behind" the main crank-pin:
/Axle
B Go Ahead
\>i Or
TcBadTU;
Pin
Fig. 3. — Location of Stephenson Eccentrics on Axle, in
Relation to the Crank-Pin.
Fig. 3 is intended to represent the Stephenson link
and eccentrics; any movement of the link-block A,
gives a corresponding movement to the valve, so, if
the link EE should be lowered, eccentric B would
actuate the valve, and as this represents an "indirect
motion" engine — ^that is, whichever way the link-
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22 THE WALSCHAERT VALVE GEAR
block is moved it will cause the valve to travel in an
opposite direction, on account of the rocker-arms —
not shown — ^the engine would run forward. As the
wheel revolved to the right eccentric B would follow
in the same direction and one-fourth of a turn behind
the main-pin, and be said to be "a quarter behind the
main pin," which it always is with indirect motion
and outside admission valves, while with direct motion,
such as is shown in Fig. 2, the eccentric is always —
with the same kind of valve — a "quarter ahead of the
pin."
Referring again to Fig. 3, if the link EE was
raised, eccentric C would control the motion of the
link-block A, and, through a reverse action of the
rocker-arms, the valve; the engine would run back-
ward — ^to the left — and, througK the changes in con-
ditions, the "back-up" eccentric C would now be
following the main-pin; so that whichever way the
wheel is being turned the eccentric that actuates the
valve is a "quarter" behind the pin, in common
locomotive design.
On locomotives having but one eccenkic, as with
those of the Walschaert type, the eccentric follows, or
precedes, the main-pin according to the direction in
which the wheel is turning: it may do either; so,
during the course of this article when the location of
the eccentric is mentioned as being ahead of, or follow-
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THE WALSCHAERT VALVE GEAR 23
ing, the main-pin, we will assume for the sake of
clearer understanding that the engine is in all cases
running forward.
It is understood that in Fig. 2 the valve is of outside
admission; the eccentric E is just 90 degrees from
the main-pin, and the valve is in an exactly central
position on its seat — therefore without lead. If the
steam throttle ^should now be opened, this engine
could not move of its own volition, for two reasons:
the valve being centred, all ports are covered and no
steam would be admitted to the cylinder; working
singly, the engine would have to be "pinched," or
moved oflF the centre by hand, but in the case of double
power, as in the locomotive, the engine on the other
side would be in a position to start the wheels turning;
they would turn to the right, the eccentric on the
visible side would push the valve forward, and the
back, or left, port would begin to open and admit
steam to the cylinder against the back of the piston.
In starting the engine, if we should pinch the wheel
backward, the eccentric would pull the valve backward
also, and steam would be admitted to the forward
end of the cylinder, pushing the piston back in spite
of our efforts, and it would hold the main-pin on the
back dead-centre point, as it was originally, as shown
in Fig. 2. So that to make the engine run backward
the turning of the wheel to the left must be made to
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24 THE WALSCHAERT VALVE GEAR
push the valve forward — the direction in which the
piston will have to travel: and to accomplish this,
the position of the eccentric must be changed to a point
on the wheel exactly its opposite in location — 90
degrees on the other side 0} the main-pin — a quarter-
turn ahead of the crank with the wheel turning back-
ward. This would now give the proper motion to
the valve for running the engine backward, and of
course the direction is fixed: it can only run thatr
way.
Besides having no power to turn the wheel when the
main-pin is on the dead-centre regardless of how
much pressure is in the cylinder, the other reason
for the engine not starting promptly, even when
assistance should be given by pinching the wheel, is
that the valve has no lead; the edge of the valve and
edge of the admission port are not even close to line-
and-line, and the assisted rotation of the wheel would
have to push the valve a distance equal to the amount
of outside, or steam, lap, before the cylinder could
begin to receive steam through the admission port.
So that valve-advance, or lead, will be the first re-
quirement in remodelling the engine of Fig. 2.
In these reference plates we are using a "return
crank*' eccentric, which shows the exact point at which
the valve gear receives its initial motion, relative to
hub centre and main-pin, much plainer than an
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THE WALSCHAERT VALVE GEAR 25
eccentric of the Stephenson type would with its disk
and strap around the axle; and in order to give this
kind of an eccentric the advance necessary to secure
lead, or overcome the outside lap, with outside ad-
mission valves we must lengthen the return crank
slightly, but still keeping eccentric pin E the same
distance from the hub centre.
Now, we find that the eccentric is more than 90
degrees from the main-pin, and that its advance that
we have given has pushed the valve forward far enough
so that the back — left port — is opened a very little —
say, one-thirty-second (^V) of an inch; steam is thereby
admitted against the piston at the prime starting
point of its stroke — while the main-pin is on the dead-
centre, and the engine standing as in Fig. 2, with
the exception, only, that we have given it lead.
Lead is not expected to help move an engine past
the dead centre; it has somewhat the opposite effect —
that of cramping, from the main-pin to the main
shaft, or axle, — a braking effect, but this is not gen-
erally admitted. Lead not only cushions the piston
at the end of the stroke, but also gets the power of
the steam against the piston earlier at the beginning
of the stroke, and the full opening of the admission
port takes place sooner: The amount of advance of the
eccentric necessary to secure the decided port opening
for lead depends on the amount of outside lap of the
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26 THE WALSCHAERT VALVE GEAR
valve, because the advance of the valve must be exactly
the distance of lap plus lead.
In Fig. 4 we have taken the engine illustrated in
Fig. 2, and interposed the double rocker-arms be-
FiG. 4. — Simple Form of Steam Engine with Indirect Valve
Motion.
tween the eccentric and valve, so that as the eccentric
moves in one direction the valve travels in the opposite
one; to make the engine still run forward the position
of the eccentric is changed to a directly opposite point
on the wheel — right straight across, through the
centre of the hub, to the "lower quarter"; and as
the main-pin moves up-forward, the backward motion
of the eccentric will be reversed by the rocker-arms
and the valve will, as required, still have a forward
motion, admitting live steam to the back end of the
cylinder and exhausting the contents of the front
end, — either the dead steam that had been used in the
preceding backward stroke, or the s^tmospheric con-
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THE WALSCHAERT VALVE GEAR 27
tents of the cylinder if this forward movement of the
piston represented the first starting of the engine.
These changes taken together have not changed the
direction in which the engine will run.
But notice: We had lengthened the return crank
of the eccentric, placing it more than 90 degrees from
the main-pin, in order to secure lead and overcome
the outside lap of the valve; if we now use the same
eccentric the lead will be negative: instead of pushing
the valve ahead, as it would do in Fig. 2, it would
pull the valve back, to the left, in an engine like Fig.
4, giving pre-admission to the front end of the cylinder
and holding the piston back — ^with the crank on the
back dead-centre. To obtain lead with engines
having a double rocker-arm and outside admission
valves, as in Fig. 4, the eccentric must be drawn
nearer than 90 degrees to the main-pin: be less than a
"quarter" from it. The return crank must be short-
ened to secure lead.
And this proves that with any kind of valve motion
where but one eccentric is used, lead cannot be satis-
factorily derived from advancing or receding the
position of that eccentric on the main-shaft or its
relation toward the main crank-pin, unless the engine
is to run in but one constant direction; if there is to
be any method of reversion, the lead must be gotten
otherwise. The Walschaert valve gear is actuated by
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28 THE WALSCHAERT VALVE GEAR
one eccentric only, and it is set, theoretically, at
exactly right angles to the main-pin — 90 degrees from
it — and the lead is derived from the action of the
piston, through suitable connections with the cross-
head, the established lead remaining unchanged
throughout the diflFerent points of cut-off in both
forward and backward gear. The engine is of direct
valve motion when the reverse lever is in the go-
ahead position, and of indirect motion when the lever
in the back-up notch, the reasons for this becoming
apparent as the method for reversing the gear is under-
stood.
Now, let's revert our attention to the crude type of
engine shown in Fig. 2, again, for we are ready to
begin the reconstruction of its valve gear into the
Walschaert motion; we will take out the pin at the
connection between the valve-stem and the eccentric
rod and dropping the end of the latter slightly, con-
nect it to the "combination lever," — see Fig. 5.
With the combination lever in a plumb vertical
position we will also connect the valve-stem to its
extreme upper end, and while the combination lever
remains at right angles to the valve-stem, the distance
from eccentric to valve is not changed and its attach-
ment has had no effect on the valve, which is central
on its seat with both admission ports covered; but if
we move the lower end of the comHnation lever
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THE WALSCHAERT VALVE GEAR 29
forward it will shorten the distance from eccentric to
valve, or move it backward and the distance will be
lengthened, and this shortening or lengthening of
the line of motion will cause the valve to be displaced^
Fig. 5. — Simple Form of Steam Engine with the Wal-
schaert method of Providing Lead.
either forward or backward, and open, somewhat, the
front or back steam admission port enough for the
lead.
All true levers have three points for the reception
and delivery of power: at one point the original
force is applied to the lever, while the other two are
the resisting and transmitting points. We have the
two latter points located as the connections of eccentric
rod and valve-stem to the combination lever, while
the point of application of power is at the lower end.
As it is the duty of the combination lever to modify
the motion that the eccentric delivers to the valve, we
must now connect the lower end of this lever to a source
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30 THE WALSCltAERT VALVE GEAR
of power in such a manner that its "interference"
with the valve will be in the proper direction.
We must now disconnect the main rod from the
main-pin and move the cross-head forward until the
piston is known to be in the exact centre of the cylinder,
and then connect the lower end of the combination
lever (still in a plumb perpendicular position) with the
cross-head by means of a short link-bar; now draw the
cross-head to the back end of the guides again, and
re-connect the main rod to the main-pin; we have
now developed the engine far enough to be represented
by the sketch in Fig. 5; the angle assumed by the
combination lever has pushed the valve forward a
distance that slightly uncovers the back admission
port; and thus the Walschaert valve gear derives its
lead — permanent lead, too, unaffected by any further
changes in the gear that may be necessary in shorten-
ing the cut-off by the introduction of reversing
mechanism.
If the outside lap of the valve amounts to one (i)
inch, and the required port opening for lead is one-
thirty-second (^) inch, the distance between the
vertical lines through the centres of the pin holes in
the upper part of the combination lever must — as the
engine stands in Fig. 5 — be just one and one-thirty-
second (lA) inches, equalling lap plus lead.
As the engine starts forward under her own steam
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THE WALSCHAERT VALVE GEAR 31
we will note the results at each quarter-turn of the
wheel. It must be remembered that the valve is
acted upon by two distinct forces: the main pro-
pulsion, for its long travel, but this motion is qualified
by the influence of the cross-head, exerted through
the combination lever, and which would give a
short travel to the valve even if the eccentric should
be disconnected. When the crank — the main-pin —
reaches the upper quarter where its leverage force is
greatest the lower end of the combination lever is
at the middle of its travel, and it would again stand
plumb perpendicular but for the eccentric now being
at its farthest point forward, and this has carried the
valve to the finish of its forward stroke, leaving the
back admission port and front port for exhaust wide
open; the crank proceeds in its turning motion and
when it has reached the forward dead-centre and the
piston is at the front end of the cylinder, the eccentric
will be at the lower quarter, and the valve would be
once more centred on its seat — but for the alterative
effect of that combination lever: its angle will be the
reverse to the position of the lever as shown in Fig.
5, with the result that the distance from eccentric to
valve will be shortened by that angle, and the valve
drawn back exactly one and one-thirty-second (isV)
inches (we are assuming that the valve has one (i)
inch outside, or steam, lap, and one-thirty-second (A)
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32 THE WALSCHAERT VALVE GEAR
inch is expected to be the amount of port opening for
lead), thus opening the forward port for the pre-ad-
mission of steam at the beginning of the back stroke
just the same as it was given at the other end of the
cylinder.
That is, the lead would be the same at the end of
each piston-stroke, if the line of motion from eccentric
to valve was a straight, horizontal level, which, in our
ideal engine, it is not; in the practical design, however,
this error is corrected, and our imagination must
supply the deficiency until our valve gear is technically
completed.
Just as the main-pin passes the bottom quarter and
the eccentric is at its farthest point on the back stroke,
the upper end of the combination lever still inclines
backward and has drawn the valve to the finish of its
backward stroke, with the front port opened for full
steam admission and the back port open from the
cylinder to the exhaust; a quarter- turn more brings
the whole gear back to the original positions of the
several parts as presented in Fig. 5.
We have described the action of the gear at four
points in the revolution of the driving wheel — a com-
plete cycle of motion — but those four points were
taken at times when the steam ports were either
wide open or only opened the distance required for
lead; intermediately between those points occur the
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THE WALSCBAERT VALVE GEAR 33
interesting phases of cut-off and release^ and further
along in this book diagrams will be found, illustrating
in a way most easy of comprehension the positions of
the different parts of the Walschaert valve gear at nine
particular points: a technical but plain analysis of
the gear, in connection with both inside and outside
admission valves. (See folder plates, Figs. 35 and 36.)
It would be better, however, to defer the study of those
diagrams until we have introduced the reversing
mechanism, and built up the complete engine.
We have already completed a very nice working
engine of the stationary type, but we must supply a
method of shortening the travel of the valve so as to
restrict the steam port openings when the engine is
running fast or under a light load, — ^this for the sake
of economy; while the means provided for so short-
ening the valve travel will, further, permit the com-
plete reversion of the direction in which the engine
will run.
For this we will cut the eccentric rod at about the
point marked X in Fig. 5, and that part of the rod
that is still connected with the return crank we will
continue to call the eccentric rod, but the front section
of the rod that connects with the combination lever
will be referred to as the "radius rod.'* The word
radius is applied to the distance from the centre to
the circumference of a circle: a spoke of a wheel, for
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34 THE WALSCHAERT VALVE GEAR
instance, measured out from the hub centre to the
periphery; one end of the radii is a fixed point, — the
forward end of the radius rod is "fixed" at a point on
the combination lever — ^with its other end rotating
about it, — the back end of our radius rod will have a
limited distance for rotation also.
The common double-eccentric gear — the Stephenson
motion — ^has a "floating" link, with no fixed, unyield-
ing point of resistance, and the pin by which it is
suspended is not exactly in the centre of the link
saddle, and from the latter fact and that at nearly every
point in the cycle of motion, at any degree of cut-oflF,
the action of the link is influenced by both eccentrics, the
link describes those peculiarly curved lines of mo-
tion that are so mystifying to the student of valve gears.
With our single eccentric we are going to do away
with a whole lot of those Unes, and we will take that
same old style of link and put the saddle-pin in the
centre of the saddle and the Unk, and attach the pin
to a fixed bracket, so that with no other connections
the link could be rotated around on its pivoted centre.
With the Stephenson motion the curve of the link
is made on a radius from the main axle upon which
the eccentrics are mounted, so that as the Unk may
be raised or lowered any point within it will be at a
constant relative distance from the eccentric centre;
the Walschaert eccentric, however, does not control
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THE WALSCHAERT VALVE GEAR 35
the radius of the link, and because the link does not
change its position in relation to the axle, the curve
need not be as it was, and we have reasons for curving
it in the opposite direction — reasons soon to be shown.
First, we will hitch-up the link; we have suspended
it at a point where, by setting it in a vertical position,
its lower end can be connected to the eccentric rod,
and having made this connection we have given a
definite motion to the link; it is somewhat as though
we had left the "back-up** eccentric, only, of the
Stephenson gear still in connection with the link.
The link-block too has been retained, and to it we
will attach the back end of the radius rod (see Fig. 6) ;
now it will be apparent why we curve the ends of the
link forward: with the link in a vertical position, as it
stands, it must be possible to slide the link-block up
and down from one end of the link to the other, carry-
ing the end of the radius rod with it without produc-
ing any motion whatever at the front end connection of
the radius rod with the combination lever. To make
this possible the forward curve of the link must have
a radius equal to the length of the radius rod. We
have now completed the design of the Walschaert
valve gear so far as it is represented by Fig. 6,
except in supplying the mechanism by which the
reverse lever may shorten the cut-off and reverse the
motion.
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36 THE WALSCHAERT VALVE GEAR
In Fig. 6 the link-block and radius rod are at the
lower end of the link, and there is, in effect, a straight
line of motion from eccentric to valve, by which we
have for the time a direct motion engine. As the
wheel turns forward the eccentric will move the valve
forward, just as if the link was not in the gear at all.
If, however, the radius rod should be raised to the
upper end of the link, the link itself would perform
ToSaratwLmr
Fig. 6. — Building up the Walschaert Valve Gear.
the functions of a rocker-arm and the forward motion
of the eccentric would draw the valve back; that would
admit steam to the front end of the cylinder, and the
wheel would have to turn the other way — ^backward —
and then the eccentric would also turn backward, the
link would change that direction of motion and again
push the valve forward, admitting steam to the back
end of the cylinder as it ought, showing that to reverse
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THE WALSCHAERT VALVE GEAR 37
the direction in which the engine runs it is only neces-
sary to change the position of the back end of the
radius rod to the opposite end of th^ link.
This raising and lowering of the radius rod and
link-block is accomplished by connecting the bar that
was once the link hanger to the radius rod, and when
the reverse lever is thrown in forward gear the link-
block goes down in the link, instead of the link itself
sliding down on the block as it does with the Stephen-
son gear; and when the reverse lever is placed in a
notch back of the centre of the quadrant the link-block
rises to a point above the centre of the link, carrying
the radius rod with it, so that when the eccentric
moves in any given direction it will move the valve
in the same or the opposite way according to whether
the radius rod is below or above the centre of the link.
In Fig. 6 the engine is in full gear ahead, and the
valve is given its full travel; in order to shorten the travel
and thereby secure earlier cut-ofifs of admission and
release, the reverse lever is hooked up nearer to the
centre of the quadrant, and the closer the link-block
will be placed to the fulcrum pin at the centre of the
link, the shorter will be its travel forth and back, with
the consequent shortening of the motion of the valve
until, with the reverse lever in the centre notch and the
link-block pin centred exactly with the fulcrum pin
of the link saddle, the radius rod has ceased its motion.
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38 THE WALSCHAERT VALVE GEAR
and there will be no movement of the valve except
that which is received from the motion of the com-
bination lever.
With the Stephenson link motion the amount of
lead given to the valve in full gear is steadily increased
as the reverse lever is hooked up, and that is considered
by many men to be one of its bad features; hooking-up
with the Walschaert gear does not increase the lead,
because it is obtained from the cross-head, and that
is one of the desirable features that recommend this
gear. If the motion work has been correctly designed
and "set up,'' and particularly if the eccentric rod is
of the correct length, when the engine is standing on
either dead centre the reverse lever can be shifted
from the farthest go-ahead position clear over to the
back comer notch of the quadrant without disturbing
the position of the valve, and this is because the eccen-
tric at a point directly above or below the centre of
the main axle holds the link in a vertical position, and
any point in the link at which the link-block may be
stationed will be at a conunon distance from the point
represented by the pin connecting the front end of the
radius rod with the combination lever — due to the
curve of the link.
If we should set the reverse lever in the centre notch
of the quadrant and have the engine moved by "pinch-
ing," or towing, as before stated, the eccentric would
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THE WALSCHAERT VALVE GEAR 39
not give any motion to the link-block, radius rod, nor
valve, but the cross-head would, by means of the
combination lever, give the valve a short travel that
would be equal to twice the distance of lap plus lead.
The connections from cross-head and valve are made
to opposite ends of the combination lever, and it is
plain to see that when the piston is at either end of its
stroke, the valve will be as far in the opposite direction
as the angle of the short end (distance between vertical
lines through the upper two pin holes) of the combi-
nation lever will carry it; this, as has been explained,
is the distance necessary to overcome the amount of
lap and then give the opening for lead, at each end of
the stroke.
This method of reversing the valve motion of a loco-
motive is referred to- by the English Professor, Mr.
W. E. Dalby, in his most interesting book on Valves
and Valve Gear Mechanism as "The Heusinger Von
Waldegg, or Walschaert, valve gear." Where, and
how, Herr Von Waldegg gained a claim to the dis-
tinction of having his name used in connectioa with
a gear for which a patent was indirectly granted to
Egide Walschaert is not explained by Professor Dalby.
Our engine is not perfect yet, as it stands in Fig.
6; there is an error to be corrected. Let us refer
again to Fig. 2, the simple form of engine that we
built up from, and we will note that the total "throw"
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40 THE WALSCHAERT VALVE GEAR
of the eccentric — ^the diameter of the circular path in
which it travels — must be of the same length as the
full travel of the valve, as there is nothing intervening
to shorten or lengthen the motion; and this equality
of motion is carried on, through Fig. 4 where both
focker-arms are of the same length to the nearly
finished construction in Fig. 6 — ^providing the engine
shown in the latter plate is in full gear either way;
and the correct full travel of the valve should be of the
same distance as the throw of the eccentric, but —
note the error:
If this engine should be moved one-quarter turn
ahead, placing the main-pin on the upper quarter, the
lower end of the combination lever would then be at
about the middle of its path of motion, but the eccen-
tric being at its farthest stroke ahead, the upper end
of the combination lever would also have its farthest
inclination ahead and the resultant angle would
lengthen the line 0} motion between the eccentric and
valve; this increases the travel of the valve at its for-
ward stroke, and is the result of the method of obtain-
ing that advance of the valve necessary in overcoming
the lap, even if the lead, as pre-admission of steam, is
not desired.
Move the engine so that the main-pin is on the
lower quarter and the eccentric at the end of its back-
ward stroke and the opposite effect will be produced;
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THE WALSCHAERT VALVE GEAR 41
the combination lever, centred at the lower end, will
incline backward at its top end and the angle assumed
in this case will shorten the distance from eccentric to
valve, and this, on the backward stroke, increases
the travel of the valve in that direction.
So, if the full travel of the valve and the full throw
of the eccentric are to be maintained as equal dis-
tances — ^and they are — ^then the valve in Fig. 6
overtravels in each direction; we have not allowed
for that and the question is. How can the travel of the
valve be correctly shortened up and not create any
other interference with the motion? Shortening the
throw of the eccentric by changing it to a point nearer
the hub centre would take away the increase of travel
that was developed in securing the advance of the
valve, — ^would it not ?
Certainly; that would be a good way out of the
difficulty — ^if we hadn't a better one: we can secure a
double result in overcoming the error — "kill two
birds with one stone."
With this gear the link generally sets rather high —
higher than appears in the sketch — and when the
eccentric is on the lower quarter there is a great and
undesirable angle between the eccentric rod and
the line of the valve-stem; horizontal lines through
the centres of the main axle and the pin connecting
the eccentric rod to the link are too widely apart, and
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42 THE WALSCHAERT VALVE GEAR
the result is an angle great enough to disturb the correct
transmission of motion. So, let's leave the throw of
the eccentric and the required full travel of the valve
remain equal, as they should be, and now extend an
arm down from the lower end of the link and connect
the eccentric rod to its lowest point instead of to the
link itself. We have completed the Engine Practical
now, as it appears in Fig. 7, in which it is seen that
with the reverse lever in full forward gear, the radius
rod as far down in the link as it will go is not in line
with the eccentric rod ; this change has shortened the
swing of the link and the carry of the link-block, and
on some engines this foot of the link is so long that the
reduction in link-block travel amounts to a great deal,
but it only afifects the long motion of the valve and does
not interfere with the amount of lead supplied by the
combination lever.
We have completed our task of erecting a design of
Walschaert's valve gear that is applicable to an
ordinary locomotive, and it is presented in Fig. 7
for technical study; it is of the same general type as
the one we built up, in Fig. 6, corrected, with the
position of the piston changed to the forward end of
the cylinder. A vertical line is drawn through the exact
centre of the valve seat and another similar line through
the centre of the valve. The valve is shown displaced
the distance required to open the admission port the
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THEWXLSCHAERT VALVE GEAR 43
amount required for lead by the angle of the com-
bination lever, and this advance of the valve is equal
to the distance between the vertical lines through
valve and seat; if now the combination lever were
disconnected at its lower end from the cross-head —
cut ofif from the influence of the piston — and drawn
to an exactly vertical position, both pin holes at its
upper end would be vertically even, and the centre
lines through valve and seat would coincide, the valve
being central on its seat and the lead eliminated.
With an engine standing as in Fig. 7, the propor-
tions of the combination lever must be such that the
distance between vertical lines through the two pin-
holes at its upper end must be the same as the distance
between the vertical lines through the valve and seat
as shown, with the valve moved back far enough to
open up the admission port the resolved amount for
lead; and this distance between centres of valve and
seat must cover the measurements of both lap and lead.
Ideally, the position of the Walschaert eccentric is
fixed at 90 degrees of the wheel circle from the main-pin,
and if the foot, or lower extension that we have supplied
to the link to which the eccentric rod is connected,
was long enough that when the main-pin was on a
dead point and the link was standing vertically the
pin in the link-foot connection of the eccentric rod
would be on a horizontal line through the centre of the
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44 THE WALSCHAERT VALVE GEAR
main axle, then the relative positions of eccentric and
main-pin would be as stated; but the link foot seldom
extends so far down, and to correct the results of the
angle so produced in its effect on the motion of the
link and valve, the eccentric is set closer to the main-
pin than 90 degrees; this point will be more clearly
explained and illustrated later on.
The oscillating link of the Walschaert valve gear
differs from the shifting Unk of the Stephenson t)rpe
constructively as well as in the direction from which
its curve radiates. Fig. 7a illustrates a style of
the Walschaert link that approximates the standard
type that has been adopted by locomotive builders
in this country, and is used, with only such variations
as variance in the general engine design may render
necessary, by the American Locomotive Company on
all of their engines equipped with the Walschaert gear
at this time, exactly as shown in the plate.
While the Stephenson link is an open, one-piece
affair, and is simple in construction, suspended by a
pin in the link-saddle on one side only, it is usually
considered necessary for the Walschaert link to be
supported by a trunnion on each side as a furtherance
of stability. In Fig. 7a, the piece that forms the
link is shown in side elevation ^4 as la, and in end
view jB as 16, and is forged from wrought iron that is
afterward case-hardened. Referring to view B, the
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THE WALSCHAERT VALVE GEAR 45
two bracket pieces 26 are shown to be bolted to the
link' piece, one on each side, their edges apparent in
section A as 2a, where they widen out to cover the
link, although the central spread is to strengthen that
part of the bracket which is the frame work of the
link. These link brackets are cast steel, and each
piece includes in its casting a trunnion, 36, in its exact
centre, around which is pressed a case-hardened.
Fig. 7. — Walschaert Valve Grear Complete. Sectional
elevation of valve and cylinder.
wrought-iron bushing; it is by these fulcrum-pins, or
trunnions, that the link is suspended from a fixed
point. At the lower extremity of the link piece-—
the ]ink foot — is a pin hole, 4a and 46, to receive the
pin that connects the eccentric rod with the link, and
this hole is fitted with a wrought iron bushing that is.
case-hardened. The reduction of the diameter, of
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46 THE WALSCHAERT VALVE GEAR
these pins and pin holes from wear is but slowly
eflfected if kept well lubricated, and is one reason
why lost motion is so slow to develop in the Walschacrt
valve gear. Just above the pin hole 4a there is an
oil well finished in the top of the link foot, if inches
in diameter by if inches deep, with a J-inch hole drilled '
down from the bottom and through the bushing.of the
eccentric rod pin hole for the feed of the oil; a threaded
cap nut is screwed into the top of the oil well as a cover.
In section A the dotted arc Unes 6a show the outlines
of the opening, or slot, in the link in which the Unk-
block travels, and the faces of this link-slot, is kept
lubricated from an oil well in the top end of the link
piece, this oil well being shown in dotted Unes at 5a
and 56; it is covered by a cap nut that is a mate to the
cover of the other oil well in the link foot, and has a
threaded tap if inches in diameter. In section B,
the left side of the link is turned to the outside of the
engine, and the hole in the outside bracket at 7a and
76 is to permit direct oiling of the link.
The link-block is represented in sections C andZ);
C is the side view and shows the block in the position
in which it would lie in the view A of the link, —
imagine the link-block C raised, following the arc
of the link until it entered the slot shown by the dotted
lines 6a. Taking an end view, if the link-block, as
shown in the section D, should be placed in the slot of
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THE WALSCHAERT VALVE GEAR 47
the link piece of section B, it would be seen that its
edges were almost flush with the sides of the link
piece— extending only ^S inches out from each side of
the link. It will be seen that the link-block contains an
oil well, shown by the dotted lines at 9c and gd, 1 inch
in^ diameter by i\ inches deep, with a J-inch feed hole
from it down to the link-block pin.
The radius rod lies in an exact line with the link,
but at its union with the link the radius rod is forked,
its jaws passing, one on each side of the central link
piece, and inside of the bracket sections at 00. There
is a pin hole through each jaw of the radius rod by
which it is connected to the link-block, the pin that
passes through the radius-rod jaws also going through
the hole &;, 8rf, of the Unk-block, and this hole is
supplied with a case-hardened, wrought-iron bushing
as a protection against wear; but there will be no
wear to the holes through the jaws of the radius rod
for the reason that a bolt runs down through a hole
in each jaw and through the link-block pin, thus
holding the pin rigid with the radius rod and turning
only in the hole through thfe link-block. The openings
7a, 76, in the outer link bracket, besides giving access
to the link slot for oiling, may also be used as an aper-
ture through which the link-block pin can be removed.
Certain types of engines are so constructed that the
eccentric rod is not in Une with the link and cannot be
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Fig. 7a. — ^The Walschaert Link.
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THE WALSCHAERT VALVE GEAR 49
connected directly with the link foot — such as the
Baldwin engine built for the Rock Island Raiload,
shown elsewhere in these pages — ^where the valve
chest lies nearer the centre line of the engine than is
usual; in such cases the link piece la, 16, extends
scarcely lower than its supporting brackets and there
is no link "foot." The trunnion, 36, on the inner
side is also dispensed with, while the outer trunnion
is made considerably longer and extends through a
sort of journal box in the manner of the common
rocker shaft, and to its outer end is attached an arm,
or lever, to the lower end of which the eccentric rod is
connected at the same distance below the centre of
the link trunnion, or fulcrum, as it would be if regularly
connected with the link foot.
While the foregoing mattet covers the standard
method of application of the Walschaert valve gear by
American locomotive builders, there are variations, and
referring to Fig. 8, it is seen that Auchincloss — ^whose
book on various valve motions is considered an author-
ity — sets the eccentrip a quarter behind the main-pin
instead of ahead of it as is usual with outside admission
valves; but he reverses the effects of that change by
carrying the link-block at the top end of the link when
the engine is to run forward. The reversing shaft is
below the link (like the old-time Rogers engines were
fitted), with the lifting arm extending backward so
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50 THE WALSCHAERT VALVE GEAR
that throwing the reverse lever forward raises the
radius rod, and the valve's action remains the same
as with the style of gear adopted by American builders
that we have analyzed. The Auchincloss type is
common on European engines.
Fig. 8. — Walschaert Valve Gear. (Illustration from Link
and Valve Motions. — Auchincloss.)
During the years that foreign railways have had the
advantage of the use of this worthy device we have not
been altogether blind to its merits : Certain progressive
engine builders and master mechanics in America
have endeavored to bring the Walschaert valve gear
to trial, and some form of it was applied to quite a
number of engines but never received a fair showing.
Men were intrusted with setting-up the gear and
maintaining it, and obtaining results from its use,
that had found it the struggle of a half lifetime to
master the mysteries of the Stephenson link motion,
and, having learned it, placed an extravagant valuation
on the mechanism that had been so hard for them
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THE WALSCHAERT VALVE GEAR 51
to thoroughly understand : and to find something better,
that was as simple as the motion of Walschaert
was hurtful to their self-conceit, and it was this priest-
craft among railroad mechanics, and even officiak, that
choked down the honest endeavor of those who did
try to improve that most vital part of the motive power
of our railways. When William Mason presented a
design of the Walschaert valve motion finely suited to
the conditions of American locomotive construction,
together with a paper detailing the good features of
the gear, to the Master Mechanics' Convention in 1885,
it met with a cool reception; in fact, without data of
actual performance in evidence, the Wakchaert motion
was there generally condemned. The time was not
ripe; they could afford to neglect it.
Shortly after this the railroad with which I was
connected was supposed to have tested the merits of
the Walschaert gear by putting that style of link,
reversing gear, and combination lever on an engine
that had been equipped with the Stephenson motion,
but instead of connecting the Wakchaert link with
an outside crank on the main-pin, one of the old
eccentrics on each side was used to operate the linjcs,
and thereby one of the best features of the device was
omitted, and neither was it erected with reference to a
scaled model. After a short time the old gear was
restored, and there were no data afterward obtainable
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52 THE WALSCHAERT VALVE GEAR
to prove the success or failure of the half -constructed
gear.
When it is decided to apply the Walschaert valve
gear to any certain type of engine the design should
be correctly laid out and constructed from a diagram,
as the proportions cannot be tampered with by ex-
perimental changes without seriously affecting the
correct working of the device. The only part capable
of variation in length is the eccentric rod which con-
nects the return crank with the Unk; this rod may
be slightly lengthened or shortened, to correct errors
in the location of the link centre, from centre of the
driving axle which carries the return crank. This
crank, representing the eccentric, must be permanently
fixed to the main-pin, and the slightest variation in
its position relative to the main-pin will be detrimental.
When the engine is assembled, the throw of the eccen-
tric should be checked up by the specifications, and
any error should be at once reported in order that the
mistake may be rectified by either correcting the
position of the eccentric, or by a change in the design
of the other parts to compensate for the error. It is
probable that inattention to this absoluteness of detail
required in the erection of the gear, as well as preju-
dice, is accountable for the condemnation of the
Walschaert motion in the past.
Along in the early seventies the Mason Machine
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54 THE WALSCHAERT VALVE GEAR
Company built quite a number of engines like the one
in Fig. 9, and one — ^an exact duplicate of the one we
present — ^was bought by the line on which I received
my first railroad experience; her performance is a
legend among the older employees of that road to-day;
the work that engine was capable of doing as com-
pared with other engines with the same-sized cylinders
was almost unbelievable, and was never equalled
before, nor since. Finally her boiler exploded near
the roundhouse at the main terminal, and she was
never rebuilt.
The engine was of the double-truck class, with
boiler, cab, and tender on one common main frame,
while the cylinders were carried on the separate driving-
wheel frame that was free to rotate on its centre be?iring
that supported the forward end of the main frame,
and it was through this centre bearing that the steam
pipe passed, the exhaust pipe being made flexible.
The entire weight of the engine was on the driving
wheels, and the adhesion of those small wheels to the
rails was unusually great and aided the power that
was developed; but it is in the cylinders that the
power of the engine originates, and they were not
large — 16 inches by 24 inches — ^and I believe that
the correct distribution of steam by a properly designed
and worthy style of valve gear had much to do with the
production of power; the results were obtained, all right.
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THE WALSCHAERT VALVE GEAR 55
It will be noticed that the reversing shaft in this
Mason engine lies over the top of the boiler, and the
bar connecting the lifting arm with the radius rod is
abnormally long, whereby, as the ends of the link are
swung forth and back, the link-block is carried in a
line very near to horizontal.
In Fig. 10 is illustrated the revised design of the
Walschaert gear that was presented and described at
Fig. 10. — Mason's Improved Design of Walschaert 's Valve
Gear.
length before the Master Mechanics' Convention in
1885. Although a D-slide valve is used, the position
of the valve chest is further in toward the centre line
of the engine than is common, this inlying being more
common to valves of the piston type. In order to de-
liver the motion of the combination lever to the valve-
stem, the upper end of the combination lever is con-
nected to the outside of the block Q which is bolted
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S6 THE WALSCHAERT VALVE GEAR
to the sliding guide-bar RS and a pin extends inside
from block Q far enough to engage with the end of
valve-stem T; this detail, however, is of the lesser
importance.
The greater import attaches to the mo4e of sus-
pension of the radius rod NP: While the suspension
bar of the engine in Fig. 9 is longer than is found on
any other engines using the Walschaert gear, Mr.
Mason went to the opposite extreme in this, his later
design, and in Figure 10 the suspension bar UV is
not more than one-half of the length of the link itself.
It was found that the point of suspension had a great
influence on the motion delivered to the valve, and
this point regularly varied in most types of the gear
from the effect of the different angles assumed by the
reversing arm that raises and lowers the suspension
bar, and also, in the case of double-truck engines like
the one represented in Fig. 9, by the rotation of the
driving-wheel frame while rounding a curve in the
track. In the plan of Fig. 10, however, there is a
stationary, curved link, or guide W taking its radius
of curvature, Uke the main reversing link, from the
pin P and also containing a sliding block which is
attached to, and worked by, the connecting bar from
the reversing arm. The upper end of the short sus-
pension bar is connected at U with this sliding block,
and at V its lower end is attached to the radius 'rod;
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. THE WALSCHAERT VALVE GEAR 57
the pin U becomes the suspension point, and its arc
of movement is equidistant from the arc of the main
link-block, as the engine stands in Fig. 10, during
all points of cut-off. The effect of this arrangement
was expected to be the nearly uniform distribution of
steam to and from the cylinder. It causes a remark-
able slip of the link-block at each end of its stroke in
working gear, either going ahead or backward, that
was expected to equalize the alternate port openings,
and it certainly does delay the motion of the valve at
the end of its travel, holding the admission and exhaust
ports more nearly fully opened at the time that they
should be so.
In American locomotive design outside admission
Xalves are generally of the plane seat, D-slide type,
while for inside admission piston valves are, of course,
the only kind used, yet the piston valve may be, and in
a few cases is, specified for outside steam admission;
but, in the latter case, the balancing of the steam
pressures against the valve pistons being less perfect
on account of the lessened area exposed to the live
steam pressure on the back valve piston, due to the
entrance of the valve-stem at that end of the steam
chest.
Up to this time we have considered the Walschaert
gear in connection with outside admission slide valves,
while as a matter of fact, at this date the majority of
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58 THE WALSCHAERT VALVE GEAR
American locomotives equipped with Walschaert's de-
vice have inside admission piston valves, the builders, or
purchasers, not taking the hint from European practice
that the D-slide type of valve may be a component
part of the Walschaert theory. To those who only
understand this motion as far as our article has pro-
gressed, it may seem only necessary to reverse the
positions of certain points of the gear in order to make
the change from outside admission to inside admission
valves, or vice versa; but that is not quite all that is
necessary to secure the same motion and valve events;
the change made in the connections to the combination
lever and shifting the position of the eccentric has a
result on the motion imparted to the valve that must be
corrected.
It may be unfortunate that the Walschaert gear is
coming into its own — ^if it can hold it — at just the time
when the piston valve is a "fad" that like the proverb-
ial dog must have its day. The combination of the
two devices is not pleasing and is likely to detract from
the good reputation that the Walschaert motion un-
hindered can make for itself.
It may be a pertinent question, just here, to inquire
what are the advantages of the piston valve that was
tried and discarded years ago, over the D-slide, plane-
faced valve that has given, and is giving, such good
service on all classes of engines. It is claimed that the
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THE WALSCHAERT VALVE GEAR 59
piston type is the only perfectly balanced valve. But
is it? The parts to be balanced are those parts of the
valve that confine the live steam; that the live steam
presses against the valve seat; the parts that make
the steam joint. Where is the piston valve balanced ?
It is only balanced where the live steam bears against
its vertical sides, and in this respect, with outside
admission, it has no gain over the D-slide valve, which
also has sides fore and aft of equal area; and piston
valves of inside admission have only the advantage in
balance that is indicated by the absence of the inter-
fering area t9.ken by the valve-stem, and this is of small
moment.
An unbalanced D-slide valve does have an enor-
mous frictional resistance to movement on its seat
due to the great area on top of it being eicposed to
the full pressure of live steam, but very few of such
valves are in existence to-day, and probably none on
the large, modem class of engines. The D-slide
valve can be, and is, most nicely balanced, and may,
if desired', have a balance of 100 per cent, which is
not preferable, as the lifting effect of the exhaust
steam under the valve must be counteracted upon.
With piston valves what stands between the enormous
boiler pressure of steam that is now carried and the
valve seat? The answer is "the packing rings."
Are the packing rings balanced? They are not, and
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6o THE WALSCHAERT VALVE GEAR
cannot be, balanced. The grooves into which the
rings are fitted must not be made absolutely steam-
tight, and they fit looser as they wear; the live steam
against the rings will go either under or over them:
If the steam passes between the rings and the walls of
the valve chest there will be a bad blow, and waste of
pressure, — no packing. If the steam finds the other
side of the rings, the rings will be pressed against the
walls of the valve chest and the opposite side of the
groove, and pack with a steam-tight joint, but with
enormous unbalanced pressure. Calipering the in-
side diameter of the valve chest after piston valves
have been in service for some time will prove the very
great wear — ^greater toward the centre — and I have
had the opportunity for feeling how hard it is to hook
up such an engine under heavy throttle.
Fig. II. — Piston Valve Actuated by Walschaert Gear.
In Fig. II we have presented a type of the Wal-
schaert gear as applied to one of the latest built and
heaviest freight engines in America, together with a
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THE WALSCHAERT VALVE GEAR 6i
section through cylinder and valve, the latter being
of the piston style, of inside admission.
With the reverse lever and link-block on their centres,
the combination lever will also be centred — ^in an
exactly vertical position — as shown in the plate, with
the main piston at the perfect centre of its stroke —
exactly in the middle of the cylinder. But the main-
pin, as may be noted, is not now precisely on the point
of *4ower quarter," the slight variation being due to
the angular position of the main rod, and if the back
end of this rod was disconnected from the main-pin,
and raised, the opening in the stub-end would centre
exactly over the hub centre.
This angular offset of the main-pin produces a
corresponding offset in the position of the eccentric
because the radii through the main and eccentric pins
are theoretically 90 degrees apart; but the eccentric
is at a point now, where its variation is at right angles to
the eccentric rod, and the deflection is of no moment.
If the reverse lever should be placed in full gear ahead^
or back, one of the steam-admission ports would be
wide open; it would, indeed, be a finely adjusted gear
in which the valve would feel the effect of that variation:
In Fig. II, notice that the eccentric follows the
main-pin by 90 degrees instead of preceding the pin
by that distance, as heretofore; also, the upper end
of the combination lever is connected to the radius
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62 THE.WALSCHAERT VALVE GEAR
rod instead of to the valve-stem, the valve-stem and
radius rod having changed places on the combination
lever. These changes are made because the engine has
inside admission valves, and as such, a valve must
travel in an opposite direction, always, to the travel
of a valve having outside admission, and the eccentric
is placed a half-turn different, or a quarter behind the
main-pin. When the piston is at the forward end of
its stroke, the front steam port must be slightly open
for the lead, and as the valve of outside admission
must be pulled back in order to open the port, the
valve with the inside admission must, conversely, be
pushed forward to get the lead opening, to secure
which action the valve-stem is joined with the com-
bination lever below the radius-rod connection, thus
having the effect of lengthening the line of motion
between link-block and valve at this juncture, and
thereby forcing the valve ahead.
With engines of the American type you can always
tell, therefore, whether an engine with Walschaert
gear has outside or inside admission valves by noticing
the position of the eccentric in reference to the main-
pin and the method of connecting the valve-stem and
radius rod to the combination lever. This is nicely
brought out in the plate representing the heaviest
locomotive ever built (Fig. 12), the Mallet, Four-
Cylinder, Articulated Compound built for the Balti-
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64 THE WALSCHAERT VALVE GEAR
more and Ohio Railroad by the American Locomotive
Company, in which the rear, or high-pressu,re, engine
has a piston valve which we may know, by reason of
the foregoing explanation, is of inside admission.
The forward, or low-pressure, engine has a plane
seat, D-slide valve,' and is necessarily of outside ad-
mission, but anyhow, we should know this on account
Fig. 13. — Diagram of Valve Gear, Low-Pressure Gear, or
Forward Section of Mallet Compound Locomotive.
of the location of the eccentric and the comiections
at the upper end of the combination lever; and in
Fig. 13 is shown an outline diagram of the latter —
the low-pressure section of the engine — ^with the posi-
tions of the combination lever and link, and the lifting
arm, at the diflFerent phases of a cycle of motion or
revolution of the driving wheel.
As an illustration of the diflFerent ideas held by
prominent American locomotive designers, compare
Figs. 10 and 11: It concerns their opposite views
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THE WALSCHAERT VALVE GEAR 65
in regard to the supposedly important point of radius
rod suspension. The Mason theory in connection
with the guide for the point of suspension is that the
suspension bar must be so extriemely short as to admit
of a pronounced swing to the radius rod. The Ameri-
can X-opomotive Company's very recent production
shown in Fig. 11, has no swing suspension whatever.
The lifting arm of the reversing shaft has a block
pivoted at its end which acts as a guide for the ex-
tended end of the radius rod, so that with the reverse
lever in either gear, forward or back, the motion of the
link as the engine wbjks catinot cause any vertical shift
of the link-block, and the only variation of the block
from a true horizontal motion will be the slight amount
due to .the angularity in the position of the radius
rod and the effect of the oscillation of the short (upper)
end of the combination lever.
The engine built for the Chicago, Rock Island &
Pacific Railroad, that is represented by Fig. 14,
was built by the Baldwin Locomotive Works, and
has the Walschaert motion and external admission,
D-slide valves, but there is a variation here from the
general manner of making the connection from eccentric
'to link: the eccentric rod is not connected directly to
the "foot" of the link, but the trunnion, or fulcrum-
pin, of the link has become a shaft, working in bear-
ings in a "box," and to the outer end of this shaft is
5
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THE WALSCHAERT VALVE GEAR 67
attached an arm extending downward and to the
lower end of which the eccentric rod is connected,
the radius rod and other parts of the gear remaining as
usual. Such variations are sometimes found necessary
for convenience in applying the gear to engines of
peculiar construction, and one of the chief recommen-
dations for the Walschaert motion is that it may be
applied to any oddly designed engine with a minimum
of change from the simplest model, and there is no
conflict to expect with other parts of the machinery:
An illustration of this, and the general adaptability
of the Walschaert valve gear, is Fig. 15, a motor-
car built for the Erie Railroad.
The locomotive exhibit at the Louisiana Purchase
Exposition, at St. Louis in 1904, included the heaviest
engine in the world, as represented by the Mallet
Compound already referred to, and another one,
typical of a class that has become renowned all over the
world for swiftness — the French De Glehn Compound :
Two engines, built for the extremely opposite in
railway service — to be the fastest and to be the strongest;
and that the valves of both are actuated by Wal-
schaert^s style of gear is proof that it was a mistaken
theory, which was held by some, that it is only on
certain types of engines, or those engaged in a certain
class of work, that the Walschaert valve gear is in
any way superior to the Stephenson link motion.
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THE WALSCHAERT VALVE GEAR 69
The fame of the De Glehn Balanced Compound
engine having reached America, the Pennsylvania
Railroad ordered one from the French builders, and
this is the one that was exhibited at the St. Louis
Exposition.
The American purchasers specified that it should be
exactly similar in design to the other engines of the
De Glehn type running on the French Unes, except
heavier, as American express passenger equipment is
much heavier than the European, and a few minor
changes in detail were necessary in order to "make
it fit" American tracks, and go where our engines will
go. In spite of the fact, however, that this engine
was built more heavy and powerful than the ones
built for the French railways, it is hardly large enough
to handle the very heavy passenger trains of the Penn-
sylvania lines, but with its proper load, with the
lighter, but fast, service on certain divisions, it has
been, and is, giving most excellent results; and the
principle upon which the De Glehn engine is
** balanced'' is now being used with success by the
Baldwin Locomotive "Works in their Vauclain Four-
Cylinder, Balanced Compound, and the Cole Balanced
Compound'engine built by the American Locomotive
Works.
Fig. 17 represents the Walschaert gear that delivers
the motion to the valves of the high-pressure cylinders
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THE WALSCHAERT VALVE GEAR 73
of the De Glehn Compound, and Fig. 18 shows the
same type of gear as applied to furnish the motion of
the valves of the low-pressure cylinders. In the
arrangement of the latter it is seea that the link is
driven by an eccentric on the main shaft; this shaft
is termed a "crank axle," because part of it is shaped
to form two cranks to which the main rods of the
two low-pressure cylinders (one on either side) are
connected, and as the entire gear of the low-pressure,
or second expansion, engine, — of the cylinders and
valves,, both — are inside of the frame, it was clearly
necessary that the eccentric should be placed on the
crank axle inside the frame, with sheave and strap
exactly like the Stephenson eccentric, except, of course,
that but oiie eccentric is used for each link. Out-
side of the frame the return crank on the main-pin
actuates the valve gear of the high-pressure engine,
which is the only part that can be seen in the photo-
engraving Fig. 16.
At this date the most powerful passenger engine ever
built is the one depicted in Fig. 19, a recent production
of the American Locomotive Company for the Lake
Shore & Michigan Southern Railroad, and of which
some of the principal dimensions are appended; here,
again, the Walschaert valve gear is in evidence; and
the heaviest and most powerful switching engine in
existence at this time, built for the same road by the
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76 THE WALSCHAERT VALVE GEAR
same locomotive company, is shown in Fig. 20, and
also is equipped with Walschaert's motion.
In all of the illustrations of Walschaert's valve gear
so far shown, as applied to American locomotives, it
will have been noticed that the link is. invariably sus-
pended from a bracket that is attached to the guide-
yoke, and the valve-stem slide is also carried by the
guides, this to insure permanency in the alignment of
the gear; but with certain types of large freight en-
gines it is sometimes inconvenient so to place the link
bracket, and the American Locomotive Company have
built quite a number of engines that have a very
large casting, extending across, under the boiler, that is
really a strong cross-brace to the engine frame at the
point where such a brace is most needed — an impossi-
bility with the common link motion — and this casting
is used to carry the link and reversing shaft. Some
engines have this brace unattached to the guides,
however, while with others it is attached rigidly to
the guide-yoke, the latter type being represented in
Figs. 20a and 20b, which are reproduced from the
American Engineer and Railroad Journal and that
journal gives the following description:
The illustrations show this new design so clearly that
it needs but little explanation, and by reference to
them it will be seen that the support for the small
crosshead connecting to the valve-stem has been
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78 THE WALSCHAERT VALVE GEAR
placed on an entirely separate guide, which is fastened
to the back valve chamber bead and through an
expansion link to the guide-yoke instead of having it
supported directly from the main guide, as in previous
designs. The bearings for the reverse shaft and the
link have beeti platced near together .in" th6 same
casting and the radius rod of the valve gear is operated
through a hanger- from the arm of the reverse shaft
instead of a sliding joint, as was used before when the
reverse shaft was supported in a bearing on the frame
between the second and third pair of drivers (as in
Fig. ii). The link itself has been made somewhat
larger and morp bearing surface given to the block.
The casting forming these bearings is fastened to a
massive but not excessively heavy steel casting extend-
ing across the frame. The construction of this casting
and its dimensions are clearly shown in the illustra-
tion. To this is also fastened the yoke supporting the
main guides. Another change is also noticed in that
the arm from the reverse sh^ft, to which is connected
the reach rod, extends downward instead of upward.
This necessitates the reach rod being placed outside
the driving wheels and on ah incline from the reverse
lever. It is supported and steadied by a guide at the
throat sheet. A change has also been made in the
return-crank connection at the main-pin for the purpose
of permitting it to be more quickly and easily removed,
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8o THE WALSCHAERT VALVE GEAR
as it has to be whenever the rods have to be taken
down. While the construction at the guide yoke
appears to be very heavy and cumbersome, a careful
examination of the drawings will show that it is really
more simple than in previous designs of this valve
gear, which were more open.
The most widely different classes of service have
been represented thus far in the showing of modem
engines that are equipped with Walschaert's valve
gear, but as a further illustration of its adaptability to
various conditions without serious alteration from the
simplest design, as well as to bring to notice the fact
that European railways are taking advantage of the
possibilities that lie in the use of this gear. Fig. 21
is presented as one of a group of thirteen engines that
were exhibited at the Exposition held at Liege in 1905,
by the State Railways of Belgium— the same road
that graduated the inventor of the motion — and this
may be said to be a lineal descendant from Walschaerjt's
successful experimental engine of 1848. It was con- .
structed by the Society Anonyme la Meuse, of Schenien,
from the designs of M. Flamme, General Inspector,
under the direction of M. Bertrand, Director of the
State Railways, and is one of a number of engines
built for experimental purposes.
The plate is reproduced directly from the June, 1906,
issue of the American Engineer afid Railroad Journal^
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82 THE WALSCHAERT VALVE GEAR
and represents a 4-6-2 engine with four simple
("simple," as the reverse of "compound," refers to
the direct use of boiler pressure in all of the cylinders
of the engine: where, no matter how many cylinders
there are, their pressures are exhausted after the first
expansive use) cylinders arranged on a horizontal
line that centres through all four pistons and the main
shaft, or axle; the main rods from all of the cylinders
drive on the front axle, two of the cylinders outside
of the frames — one on each side of the engine — having
their main rods attached to the crank-pins, while the
other two cylinders inside the frame are connected
with a built-up crank axle; but with reference to their
points of connection on the main axle the cylinders are
arranged in pairs, the outside cylinder on each side and
the one next to it just inside the frame are paired,
with the crank-pin and the crank axle of each pair set
180 degrees apart, or just opposite each other on the
shaft. With all moving parts in the cylinders, and the
main rods, being exact dupUcates in the matter of
weights per pair, the motion on each side of the engine
is perfectly balanced. The paired cylinders on one
side of the engine are connected with the main-pin
and axle crank at 90 degrees from the connections of
the corresponding pair of cylinders on the other side
for the same reason that the two main pins of the
common two-cylindered engine are always set quarter-
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THE WALSCHAERT VALVE GEAR 83
ing to each other — so that both forces can never be on
ihe dead- centres at the same time.
This plan of arranging the four cylinders and their
delivery of power is being used on some of the most
recently built American locomotives, but our engines
are compounded, only two of the cylinders receiving
boiler pressure direct: the Vauclain Balanced Com-
pound, and the Cole Balanced Compound, both
previously noted, are of this type, with the large, low-
pressure or second-expansion cylinders outside the
frame, and the smaller, high-pressure or first-expansion
cylinders located inside, or between the frames; in
starting a train— particularly a heavy one — the power
of the cylinders termed high-pressure is temporarily
suspended, thus removing an immensely twisting
effect from the cranks in the axle at a critical time, and
full boiler pressure at long cut-off is admitted to the
large cylinders outside of the frame. After the train
IS under way, and the action is changed to compound,
the inside cylinders receive direct boiler pressure and
exhaust it into the large, outside cylinders in which
the final expansive power of the steam Is obtained,
and from which the exhaust to the atmosphere' takes
place.
If the Stephenson valve gear is used on engines of
this type it necessitates placing the eccentrics on some
other than the crank axle, for there will not be room
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84 THE WALSCHAERT VALVE GEAR
left after considering the main cranks; and taking the
power to actuate the valve from any other pair of
wheels is highly undesfrable, both on account of the
extra amount of lost motion introduced and the entire
disability of the engine in case one side rod should
break, if it should be the section between the wheels to
which the niain rod is attached and the pair carrying
the eccentrics — on either side of the engine. The ap-
plication of the Walschaert gear eliminates the possi-
bility of such troubles, as this gear has no dependence
on the axle for anything, and the eccentric can always
be placed on the main pair of wheels.
The assertion that the Walschaert valve gear can
be applied to engines of odd design without addition
of complicated parts, where the Stephenson motion
would have to include so much more weight of metal
as to be almost prohibited, is proven in the case of this
Belgian engine in Fig. 21.
In this engine live steam is used in all of the four
cylinders and the operation of each is controUecl by
a separate piston valve of inside admission — a design
of valve quite unusual in European practice — and
both valves on each pair of cylinders are actuated by
but one set of WalschaerVs gear.
To glance at the set-up of the gear in Fig. 21, — the
eccentric placed ahead of the main pin and the valve-
stem connected at the extreme top end of the com-
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OF BELGIAN FOUR CYL
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OF BELGIAN FOUR CYL
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THE WALSCHAERT VALVE GEAR 85
bination lever — one would think that outside ad-
mission valves were indicated, but in this case things
are not as they appear to the eye: the motion of the
Fig. 24. — Side Elevation Diagram of Belgian Engine.
Fig. 25. — Plan Diagram of Above.
combination lever is not given to the stem of the outer
piston valve, but is transferred through a rocker-arm
to the valve operating the other cylinder of the pair —
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86 THE WALSCHAERT VALVE GEAR
the one inside the frame — and as the main rdd from
the inside cylinder is connected to the axle crank exactly
opposite the main-pin connection of the outside cyl-
inder — 1 80 degrees apart — the set-up as shown is
correct in its action on the inner half of the motion on
that side of the engine.
Now, in order to supply a satisfactory motion to the
valve of the outside cylinder it is only necessary to
give it an exactly opposite movement to that of the
inner one, and this is easily accomplished by extending
the stem of the inner valve through the front head and
connecting it to a lever that extends across the frame,
a pin in the exact centre of the lever and a bracket
attached to the frame forming its fulcrum, and to the
other end of this lever is connected the extended rod
from the outer valve, which also passes through its
front steam-chest head. This action is the same for
the pair of cylinders and valves on each side, and in
the sectional views, on folding plates. Figs. 22 and 23,
and the diagrams. Figs. 24 and 25, the valve con-
nections are clearly seen.
In American practice the rocker-arm would undoubt-
edly be dispensed with, further simplifying the motion,
and the gear so devised as to operate the outside valve
and cylinder direct, using the lever connecting the
extended valve-stems to actuate the inner valve.
The diameter of the cylinders is reduced to an
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THE WALSCHAERT VALVE GEAR 87
extent that both pistons of one pair hav^ an area
exposed to steam pressure of about the same number
of square inches as would be contained on a single
piston of an ordinary two-cylindered engine of the same
weight and steam-generating capacity, and therefore
the amount of steam consumed is the same for each
type of engine, but this Belgian locomotive with four
cylinders is. perfectly balanced, and the rods, pistons,
etc., need not be much over one-half the weight of
the corresponding parts of a two-cylindered engine.
To the name of Egide Walschaerts belongs the credit
and the honor of having first conceived the principle
of the valve gear that rightfully bears his name, but
that principle has been more highly developed by
others, until the device as it is applied to locomotives at
the present time is practically perfect; but in order to
show that there has been no actual change in the
original Walschaert theory, the following bit of history
is hete reproduced from the Railroad Gazette of Novem-
ber 24, 1905, and is contained in an article on the life
and works of the inventor, by Professor M. J. Boulvin
of the University of Ghent:
After Walschaert had obtained (through the assist-
ance of his friend, M. Fischer) his Belgian patent, he
took out another patent for the same invention, on
October 25th of the same year, in France. There also
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88 THE WALSCHAERT VALVE GEAR
exists among the documents left by the inventor a
contract signed by Demeuldre, at Brussels in 1845,
from which it appears that he undertook to obtain
a patent of importation into Prussia for the new
valve motion, subject to an assignment by Walschaert
of half of the profits to be deducted from the intro-
duction of the new valve motion in that country. It
is probable, however, that this contract was never
carried out.
The dbsign attached to the Belgian patent is repro-
duced in Fig. 26. In this primitive arrangement the
link oscillated on a fixed shaft, in regard to which it
was symmetrical, but it had an enlarged opening at
the centre so that only at the ends was it operated
without play by the link-block, which was made in
the form of a simple pin. There was pnly one eccentric,
the rod of which terminated in a short T carrying two
pins. The reverse shaft operated the eccentric rod
and maintained it at the desired height. For one
direction the lower pin of the T engaged in the lower
end of the link, and to reverse the engine the rod was
raised so that the upper pin engaged in the upper
end of the link. The angle of oscillation of the link
varied with the position of the pin in the link, and
this oscillation was transmitted by an arm to the
combination lever, which was also operated by the
crosshead.
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90 THE WALSCHAERT VALVE GEAR
The central part of the link could not be used for the
steam distribution, as it was necessary to enlarge it to
allow for the play of the pin which was not in operation.
It may be asked why the inventor used two separate
pins mounted on a crosspiece on the end of the eccen-
tric rod instead of a single pin on the centre of the
rod which would have served for both forward and
backward motion without requiring the centre en-
largement of the link. It must be borne in mind
that the raising or lowering of the eccentric rod by
the reverse shaft was equivalent to a slight change
in the angular advance of the eccentric. Consequently,
with a link of sufficient length, to keep down the
effect of the angularity it was necessary to reduce as
much as possible the movement of the eccentric rod.
Notwithstanding its differences the mechanism de-
scribed in the patent of 1844 is in principle similar to
the valve motion with which every one is to-day familiar,
and which the inventor constructed as early as 1848,
as is shown by a drawing taken from the records of
the Brussels shops, on which appears the inscription
"variable expansion; E. Walschaerts' system applied
to Locomotive No. 98, Brussels, September 2d, 1848."
Fig. 27, taken from this drawing, shows the valve
motion as we know it to-day. For although it is
true that the link and the combination lever are usually
placed in a different position so as to shorten the
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92 THE WALSCHAERT VALVE GEAR
eccentric rod and the valve-stem, yet the design of the
locomotive often requires an arrangement similar to
that shown above. The system which Mr. Heusinger
Von Waldegg invented in 1849, ^^^ which he applied in
1850 to 1851, differs only in a few insignificant par-
ticulars from that shown in Fig. 27. Walschaerts had
therefore preceded him.
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SECOND DIVISION
DESIGNING AND ERECTING THE
WALSCHAERT VALVE GEAR.
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SECOND DIVISION
DESIGNING AND ERECTING THE WAL-
SCHAERT VALVE GEAR.
When a newly equipped engine with Walschaert
valve motion is received by a railroad and after the
gear has been set up complete at the roundhouse,
everything should be carefully inspected, with the
view of securing a perfect initial adjustment of the
entire valve motion, and to eliminate, if found, any
slight error whatever while the other parts of the motion
work of the engine are new and of perfect fit and prop-
erly adjusted all around; especially in regard to the
driving-boxes, rod brasses, and other bearings. It
must always be remembered in setting the Walschaert
valve gear that two otherwise separate and distinct
motions are now brought into a working combination
with each other in order to produce the desired move-
ments of the valve, and these two motions are due to
the piston's travel, delivered through the crosshead
connection, and the throw, or turning movement, of
the eccentric.
The piston's motion really governs the lead by
oflfsetting the valve from its central position far enough
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96 THE WALSCHAERT VALVE GEAR
to overcome its steam lap and enough further to give
the amount of port opening desired for lead, and it
will do this in both front and back positions of the
piston, the lead being the same at the beginning of
each stroke, both forth and back. The piston must
move the valve in a direction opposite to its own
position in the cylinder to secure lead with outside
admission valves, but the piston must draw the valve
further in the direction tl^e piston lies in — toward the
end of the cylinder — ^to give the advance for lead with
a valve of inside admission; and this principle is made
plain by the diagram in Fig. 28, in which it is seen
that the piston is connected to one end of a common
lever, and the connection to the valve-stem is either at
the extreme opposite end, or at an intermediate point
on the tever, according to whether the valve is of
outside or inside admission. There are three points
to a true lever, however, and the third point on the
combination lever is its connection with the radius
rod — the point where the valve, through the com-
bination lever, receives the greater part of its motion
due to the eccentric's action.
In Fig. 28, two combination levers are represented
as being actuated by the piston and two radius rods,
and are operating two valves, — one with inside ad-
mission and the other with outside admission; the
latter, and upper, valve has its stem and the radius
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THE WALSCHAERT VALVE GEAR 97
rod attached to the combination lever in such a manner
that the angle given to the lever by the piston being at
the extreme end of the cylinder has moved the valve
from an otherwise central position a slight distance
in an opposite direction from that occupied by the
piston, as is required in order to open the proper ad-
mission port for lead.
Liv^ frteiirr-
Fig. 28. — Comparative Diagram of Combination Levers Used
with Outside Admission and Inside Admission Valves.
To give lead to the valve with inside admission the
valve-stem and radius rod are connected to the lower
combination lever in an exactly opposite manner to
the way in which the same connections are made on the
other combination lever just described. The angle of
the combination lever in this case pushes the valve in
the opposite direction, and the reason for this is plainly
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98 THE WALSCHAERT VALVE GEAR
seen by reference to the plate: steam admission past
the valve takes place externally with the upper valve
and internally with the lower one, yet in each case the
steam is admitted to the same end of the cylinder,
and this requires that the two kinds of valves be
advanced in opposite directions.
The Mason Machine Company undoubtedly were
the pioneers in the attempt to introduce the Walschaert
valve gear into this country, and if that company was
still in the field, their experience would help greatly
in the present-day application of the gear. The
American Locomotive Company and the Baldwin
Locomotive Works are, however, making a specialty
of supplying the Walschaert motion to their heavier
engines, and the Baldwin Company gives the following
instructions for erecting the gear and setting the valves:
I. Check carefully the dimensions of the following
parts, rejecting any that are not exactly to drawing:
a Valve .
b Valve-stem.
c Valve-stem crosshead, or slide.
d Combination lever.
e Crosshead Unk.
/ Link radius rod.
g Reverse link.
h Location of combination lever on crosshead.
k Length of eccentric crank.
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THE WALSCHAERT VALVE GEAR qg
2. Check eccentric throw to see that it is exactly as
specified.
3. Be sure that guide-bearer is correctly located from
centre of cylinder, as the reverse h'nk is usually attached
to it, and variation in the location ot the Hnk cannot
be allowed. If the link is attached to separate cross-
tie, similar precautions must be taken to insure its
correct location.
4. Exercise great care in the location of the imk, so
that the trunnion (fulcrum) centre is exactly to dimen-
sions from the centre of cylinder.
5. See that the reverse shaft centre is correctly
located to dimensions given, and that the lifting arm
and link are of the exact lengths as specified.
6. Connect crosshead gear to valve, and radius rod
to link, Tw7fcm/ connecting eccentric rod to link.
7. Hook up radius rod to exact centre of linkj and
then revolve driving wheels, seeing that crosshead gear
gives correct lead as specified for both front and
back admission ports.
(Say that A inch is the required lead : with the steam
chest open at this time — in the case of a D-slide valve
— it should be seen that when the crank pin is at either
dead- centre the admission port is open ^ of an inch.
With outside admission valves this will be plain, but
with piston valves of inside admission a very little steam
or compressed air can be used, and by marking the
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loo THE WALSCHAERT VALVE GEAR
valve-stem and noting the blow from the cylinder
cocks and the point at which the pressure ceases to
escape, the amount of lead can be closely approximated.
It should be possible, however, to obtain correct results
in this phase of the motion with the eccentric rod
connected with the link, for it is required that when
the reverse lever is at mid-gear the radius rod shall be
centred in the link, and the motion of the latter shall
have no influence on the valve nor combination lever.)
8. Connect link to return crank by eccentric rod,
and obtain full travel front and back, and in both
forward and backward motions, correcting any errors
by lengthening or shortening the eccentric rod as
previously noted.
The valves may now be considered as definitely set,
and may be tested to any cut-off points in the usual
manner.
A simple additional check should be made as foflows:
Set one side of the engine so that the piston is at its
extreme forward position in the cylinder, and check
lead on the admission port.
In this position it should be possible to move the
link-block through its entire travel in the link without
in any way disturbing the movement of the valve.
This operation should then be reversed and the
other side of the engine similarly tried with the piston
located at its extreme backward position in the cylinder.
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THE WALSCHAERT VALVE GEAR loi
If an inspection of the Walschaert gear reveals an
error it must not be regarded as a constitutional fault
that cannot be corrected; go over the motion carefully
and it will not be hard to find the cause — a cause that
probably can easily be adjusted; for, while it must be
realized that as it is impossible to perfectly "square the
circle/' and is as equally impossible to exactly convert
the circular motion derived from the driving wheel or
its axle into the straight-line motion of the valve with-
out error — especially when the results from diflFerent
points of cut-off are required to be the same in forward
gear as' with the engine reversed, in back gear —
yet the designers have found means by which those
inherent irregularities may be practically dissipated
and the errors so far reduced that after the natural
wear of the working parts has been taken up they can-
not be detected, nor will they lessen the economy or
power of the locomotive. It must not be inferred,
however, that the foregoing statements are made to
excuse any inaccuracies that may exist within Wal-
schaert's type of valve gear when turned out of the
builder's hands that render it inferior to the.Stephenson
motion as to the cut-off points, etc.; the Walschaert
motion leaves the shop with an indication of truer
locomotive valve performance than any other, ex-
cepting, perhaps, the Allan gear, which is generally
regarded as the most perfect valve motion for logo-
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I02 THE WALSCHAERT VALVE GEAR
motives in existence, but is not easily adapted to
modem American locomotive construction.
In this connection it may be well to say that a
great many persons confuse the Allan vaive gear with
the Allen valve; the former, as the words imply, refers
to Allan's improved mechanism to operate any ordinary
locomotive valve, while the Allen valve consists of a
common D-slide valve with a supplementary steam
admission port cored through it. The Allan gear is not
used in this country, but the Allen valve is quite common.
In reviewing the Walschaert principle, or in direct
inspection of the gear, keep these points in mind,
always: The motion work once set up there is no
regularly provided way for any readjustment except
by the eccentric rod; when necessary, it may be
lengthened or shortened until, with main pin on
either dead-centre, the link has assumed its correct
position, in which the reverse lever may be moved
from the back corner notch to the farthest go-ahead
position without shifting the valve, or moving it in the
least. But, as lining, or shimming-up, the bearing
supports, or carriers, affects the transmission of power,
so it may be that parts of the Walschaert gear are not
in perfect conjunction, and before the length of the
eccentric rod is altered it is well to examine the length
of the valve-stem, and it may be of advantage to
either plane-off) or line-under, |he foot of the link
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UNIVER':.rY •
THE WALSCffTiERT VALVE GEAR 103
support, which might correct the rod measurements
all the way from eccentric to valve, or else indicate
the rod that remains to be changed.
In erecting or designing the Walschaert valve motion
for new equipment it is of the utmost importance that
it shall be correctly laid out and correctly set up. In
individual cases the only accurate way is to have the
motion plotted out by an expert, but that is a slow and
laborious process, and in shops that make a specialty
of supplying this gear a models as a base to work from,
is considered a necessity. With a complete under-,
standing of the principle of the Walschaert gear,
however, the use of certain formulae will enable one
to design the motion for any class of engine, because
one of its greatest reconmiendations is that the most
pronounced changes in locomotive construction need
not involve any serious alterations in this valve gear.
Before presenting such formulae the following sug-
gestions are advisable:
The radius rod should be as long as it can be con-
veniently placed : at least eight times, or, better still,
ten or twelve times the length of the travel of the link-
block; and, of course, the radius of the link must be
equal to the length of the radius rod.
The shortest length of the eccentric rod should never
be less than three and one-half times the throw of th^
eccentric.
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THE WALSCHAERT VALVE GEAR 105
If it will not shorten the effective throw of the link
too much the connection from eccentric rod to link
should be brought down as near the centre 'Une of
motion of the main rod as can be done; but this is a
point for compromise.
The length of the long division of the combination
lever should not be less than 2J times the stroke.
The length of the combination lever must be taken
♦to suit the conditions under consideration in each
case, so that the angle through which it oscillates
will not exceed 60 degrees, but less is preferable.
The required horizontal movement or travel of the
connecting point F of the radius rod to the combination
lever for a given maximum valve travel must now be
ascertained, and is found by the following formula in
which R and C are the same as above, namely:
R = radius of main crank.
C = lap and lead.
a = half of the travel of the valve.
b = half the travel of point F.
b = — J ^ ~" — for outside admission, and
R-\- C
b = — y-^~i — ..for inside admission valve.
R — C
These may also be laid out graphically as per Fig.
30 for outside and Fig. 31 for inside admission valve
by drawing a circle with 5 as a centre ?ind a a§ radium
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io6 THE WALSCHAERT VALVE GEAR
(shown dotted in the figures). . Lay out crank radius
R to the left from S^Sd and the lap and the lead
dimension C=Se on same side of 5 for inside admission
(Fig. 31), and on opposite side of S for outside ad-
mission (Fig. 30). Draw ef and 5 A perpendicular to
Sd when / becomes the intersecting point between the
valve travel circle atid the line ef. Draw the line dj
and where this intersects the line Sh which point we
will call h (foimd by extending df in Fig. 31); Sh
Fig. 30. — Laying-out Diagram, Walschaert Valve Gear.
is then the desired dimension b in the formula, or
one-half the required movement of point -F, the total
of which is represented by the full drawn circle in the
figures.
This is a most important function of the gear upon
which practically all the others depend and is rather
complicated to find by plotting. With a correct sus-
pension of the link-block it will have the same horizon-
tal moyen^en^ as the point -F, and by limiting the angle
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THE WALSCHAERT VALVE GEAR 107
of the swing of the link to 45 degrees as a maximum
we get the rise or depression of the link-block on
either side of the link fulcrum the distance
6*
Og = .
tan. d
-. (Fig. 29)
where O is the link fulcrum, rf= one-half of the
swing of the Unk in degrees, and 6= half the travel
of point F in the previous formula.
Fig. 31. — Laying-out Diagram, Walschaert Valve Gear.
The vertical location of the Unk fulcrum O should
be, when practicable, on a line drawn through point
F parallel with the valve-stem, and the eccentric rod
connecting pin K to the link should be as nearly as
practicable on the same level as the main axle in order
to minimize the effect of the vertical play of the axle on
the valve events, but on large engines it may be found
necessary to lower fulcrum O and raise connection K
to avoid excessive throw of the eccentric crank.
* As no suspension gives a perfectly equal drop of the
block in Ipotl) }ink positions, this formula is only approximate,
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io8 THE WALSCHAERT VALVE GEAR
In locating the longitudinal position of the link
fulcrum, consideration must be given to the lengths of
the eccentric and radius rods so that both may be
approximately of the same length. When these
lengths fall below three and one-half times the total
vertical sweep of the link-block the radius rod should be
favored in preference to the eccentric rod. The exact
position of the eccentric crank must be plotted as well
as the longitudinal location of point K. The former
must bear such relation to the main crank that it
brings the link in its middle position when the main
crank is on either side of its dead-centres and the
connecting point K must be so located that it swings
the link in the required angle d on either side of the
middle position of the link; that is, in other words,
the point K should be so located on the curve it must
follow with fulcrum O as a centre that its deviation
from the tangent of the eccentric rod to this curve is
such that it, as near as practicable, compensates for
the irregularities brought about by the angularities of
the main and eccentric rods which in ordinary cases
brings it from 2 inches to 5 inches in the rear of the
tangent to the link drawn through the fulcrum O.
The locus of the suspension point of the radius rod
lifting bar must also be plotted so that the link-block
is at the same point of the link in its extreme positions
^t all cut-off§. This locus is a curve with its gentre
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THE WALSCHAERT VALVE GEAR 109
in the* vicinity of the point F when in its mid-gear
position. It would be impracticable, however, to have
a lift arm of this length, and a cutre of smaller radius
must be substituted and so applied that it intersects
with the former cur\'e at points giving the least possible
distortion to the motion, favoring the position of the
link-block in which it is mostly used in service.
The sliding lifter shown in Fig. 1 1 meets these con-
ditions better than any other method of suspension,
but, due to wheel arrahgiements of various designs of
engines, this is not always applicable but must be
substituted by swinging lifters, as appear ^in use with
nearly all the designs of valve gear that are illustrated
in this book, and which, when properly plotted,
give for all practical purposes equally good results.
The vertical height of lower connection m of the
combination lever in relation to the crosshead con-
nection has a slight influence on the port opening and
should, therefore, in the centre position of the lever,
be about in the same level as the crosshead connecting
point n (see Fig. 11).
In Fig. 32 is the motion of the valve graphically
represented by the Long diagram at different cut-offs,
where the horizontal lines represent the port opening
edges in the cylinder face, and the curves of the steam
inlet edges of the valve, showing the opening and cut-off
points where the latter intersect the former and the
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no THE WALSCHAERT VALVE GEAR
port openings at the various points of the stroke are
measured by the height of these curves over and under
the opening edges of the ports at both ends of the
valve, respectively.
It will be noticed that these ellipses are slightly flat-
tened on one side, which is caused by the slower lineal
motion imparted, to the valve relative to the angular
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Fig. 32. — Long's Diagram of Valve Events Efitected by
Walschaerts' Motion.
motion when the eccentric passes its back centre com-
pared with that of the front centre, due to the angu-
larity of the eccentric rod, and is more marked the
shorter the rod. Fully s)anmetrical ellipses are not
obtainable, as this would require the eccentric and
main rods to be of infinite length; this angularity,
however, is of but Uttle detriment to the distribution
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THE WALSCHAERT VALVE GEAR iii
of the steam as long as the relation between the length
of the eccentric rod and the throw of the eccentric is
not less than the given limitations, and is present in
all kinds of continuous valve motions derived from
uniformly rotating cranks or eccentrics.
GENERAL NOTES FOR ADJUSTING WAL-
SCHAERT GEAR.
1. Ascertain by the following method the position
of the eccentric crank: Mark the position of the link
relative to its middle position on both of the dead-
centres of the main crank. If the position of the
link is the same in both cases, the eccentric crank
position is correct; if not, the eccentric crank should
be shifted until this occurs, or as near so as possible.
2. After the eccentric crank has been* correctly set
the eccentric rod should be lengthened or shortened
as may be required to bring the link in its middle
position so that the link-block can be moved from
its extreme forward to its extreme backward position
without imparting any motion to the valve. It may be
noted that the link position may be observed by the usual
tram marks on the valve-stem, or direct by marks
on the link pin, as may be found most convenient
with the link-block in full gear — ^preferably ahead.
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112 THE WALSCHAERT VALVE GEAR
3. The difference between the two positions of the
valve on the forward and back centres of the engine
is the lap and lead doubled: it is the same in any posi-
tion of the link -block and cannot be changed by
changing the leverage relations of the combination
lever.
4. The tram marks of the opening moments at both
ends of the valve should be marked on the valve-stem
and the latter lengthened or shortened until equal
leads at both ends are obtained.
5. Within certain limits this lengthening or shorten-
ing may be made on the radius rod if it should prove
more convenient, but it is desirable that its length
should be so nearly equal to the radius of the link that
no apparent change in the lead should occur in moving
the link-block as stated in note No. 2.
6. The lead may be increased by reducing the lap,
and the cut-off points will then be slightly advanced.
Increasing the lap produces the opposite effect on the
cut-off and reduces the lead the same amount. With
good judgment these quantities may be varied to
offset the irregularities inherent in transforming
rotary into lineal motions.
7. The valve events are to a great extent dependent
on the location of the suspension point of lifter of the
rear end of the radius rod, when swinging lifter is used,
which requires that this point should be properly laid
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THE WALSCHAERT VALVE GEAR 113
out by careful plotting, or, if convenient, it is prefer-
ably determined by a model, as irregularities due to
incorrect locus of this point cannot be corrected by
the other parts of the gear without more or less dis-
tortion of same. When this point is so fixed that a
change of same is impracticable it may be better,
however, to modify other elements if thereby the
motion in general can be improved.
HELMHOLTZ MODIFICATION.
Among the various modifications of the Walschaert
gear the one made by Helmholtz is probably of some
advantage. This modification consists in making
the link straight, and the radius rod' is connected to
the lifting link instead of to the link-block. The
curving of the link is compensated for by the reversing
shaft, or lifting-arm fulcrum, being located in a given
position above the link, so that the locus of the sus-
pension point of the lifting link forms an arc of a
circle with its chord perpendicular to the centre line
of the radius rod in its centre position. The radius
of this arc bears the same relation to the length of the
radius rod as the distance of the radius-rod connection
above the link-block bears to the length of the lifting
link, which results in that this connection is moving in
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114 THE WALSCHAERT VALVE GEAR
an arc with a radius of the length of the radius rod,
and the same motion of the valve is obtained as in the
direct Walschaert gear.
Two advantages may be claimed for this modification,
of which one is the straight link being simpler to make
than the curved one^ and the other is that on large
piston-valve engines with inside admission the link
fulcrum can be lowered by the amount the radius-rod
connection falls over the hnk-block, whereby the
eccentric-rod connection can be brought closer to the
centre line of the axle with less length of link and
eccentric throw. It has, however, the disadvantage
that there is little choice in the location of the reversing
shaft, or lifting-arm fulcrum, a proper position for
which is hardly obtainable on all types of engines, and
admits of no other method of lifting the radius rod in
linking-up, or reversing, the engine.
Fig. 33 shows a combination of two diagrams:
namely, those of Reauleaux and Zeuner, which coincide
exactly as to the different valve events, which may be
found as follows:
The distance AB represents the travel of the valve
as well as the stroke of the engine, though in different
scales, which makes no. difference when the cut-off
is always expressed in fractions or per cent of AB.
The maximum cut-off is determined upon to be AR.
Draw a perpendicular line RC from AB until it cuts
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THE WALSCHAERT VALVE GEAR 115
the arc ACB. Next decide on a desired lead, and,
with that as a radius, draw an arc with -4 as a centre.
Draw a line from C tangent to the lead circle around
A, when the lap of the valve is found to be equal to
Fig. 33. — Combination of the Reauleaux and Zeuner Diagrams.
the perpendicular distance from the line CS to the
centre O of the diagram. The crank will then be in
position 05 when the valve commences to open, or
the angle -405 in advance of the dead-centre, and on
OC at cut-off. Continuing, we find the valve in its
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ii6 THE WALSCHAERT VALVE GEAR
middle position when the crank is on OG which is
drawn parallel to SC through the centre O. Extend
this line to F, and with the exhaust lap as a radius
draw the exhaust lap circle on the opposite side of the
line GF and draw DE tangent to this circle, when OD
is the position of the crank at the release point. From
this point the exhaust remains open imtil the crank
reaches the position 0£, when it closes and com-
pression takes place until it again reaches OS for
admission and one revolution is completed.
By placing the Zeuner diagram upon this, draw HJ
perpendicular to FG, and with the radius OH of the
eccentric circle as a diameter, draw the admission
valve circle OVHnO, and the lap circle with the
steam lap as a radius and find the intersection occurs
at F, both with the circles and the previously laid-
down admission line OS and the cut-off point at the
intersections at ». On the line Off set off the width
of the steam port from L toward H equal to Lm, and
with Om as radius draw the arc KniK. The shaded
figure enclosed by the letters VKK^nL represents the
steam port opening during the admission period,
and the width of the port opening at any desired
position of the crank is found by measuring the distance
radially from O between the lap and valve circles on
the port line, as the case may be, on the desired crank
position.
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THE WALSCHAERT VALVE GEAR 117
The exhaust openings are determined in the same
manner, and are shown on opposite side of FG, where
the crank passes through the arc DJE during the
exhaust period with a positive exhaust lap of the size
EF. When the exhaust edge of the valve is line and
Fig. 34.
line this arc becomes GJF, or 180 degrees, and when
a negative lap (clearance) occurs, the duration of the
exhaust period exceeds the half revolution of the
crank. The various events are indicated aroimd the
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ii8 THE WALSCHAERT VALVE GEAR
eccentric circle on the figure as they take place during
a complete turn of the crank.
In Fig. 34 the eccentric and admission valve circles
are shown at diflFerent cut-offs where each set of lines
and circles is governed by the same explanation as
those of Fig. 33 where the admission points 5, 5^ 5',
and 5* correspond to the closing positions C, C\ C*,
and C*, cut-off points R, R\ F?, I^, etc. On OH we
have the full-travel valve circle, and OL the lap, or
radius, of the lap circle, the latter being the same
for all cut-offs as well as the lead, the radii H\ H^^ Jf ',
etc., of the eccentric circles, or diameters of the corre-
sponding valve circles, terminate on a line HI drawn
perpendicular to ^45 and at a distance from O equal
to that of lap and lead.
When the reverse lever is in its centre position the
diameter of the valve circle falls on the line AB, and is
equal to lap and lead. Continuing in back position
we have the same method repeated, and 01 would be
the full-travel valve-circle diameter, or the same as
the eccentric radius for the valve travel. Any desired
cut-off position may be laid out in same manner as
that in Fig. 33, which shows all of the valve events for a
complete revolution of the axle.
In victual practice the movements are not so regular
as the circles indicate, as it is impracticable to obtain
the various loci in their theoretical positions; besides,
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LEAD
&.
3
15
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Fig. 35. DJ
ts of the drivii
Valves, actual
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e events at nine
ith Outside Ad-
Motion.
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THE WALSCHAERT VALVE GEAR 119
we have the angularities both of the main rods and the
eccentric rods to contend with, and whereby irregu-
larities are entering in the problem that must be
compensated for, as referred to in the general de-
scription. It is not to be considered that a uniform
circular motion is the best, but an approximation to
it works with less shocks or jerks, and is therefore
more desirable for so high-speed an engine as a loco-
motive. A few advantages can be taken, however,
in selecting the suspensions and various connections,
so that better results can be obtained than from a
true circular motion, which are principally affected by
three union points, and are, first, the connecting point
of eccentric rod and link; second, the locus of the
lifting- link suspension point; and third, the relative
height of the crosshead-connection point of the union
bar to the corresponding point of the combination
lever.
It is not necessary to lay out the valve diagrams
except where a given cut-off per cent is wanted. This
is the most convenient way to find the required lap.
Fig. 35 and 36, the diagrams on the folding plates,
represent the positions of the valve with the main crank
at nine different points of the revolution of the driving
wheel. In Fig. 35 th" valve is of the' piston type,
with inside admission, and in Fig. 36 an outside
admission valve is shown, of the D-slide pattern.
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I20 THE WALSCHAERT VALVE GEAR
Cardboard models of each of those valves will be
found in the pocket on the inside of the front cover,
and these models may be placed on the horizontal
lines representing the valve seats of the folder plates
and a good idea can be obtained of the work done by
the Walschaert gear in either of the two methods of
applying it, namely, to actuate inside and outside
admission valves.
Place one of the cardboard valves on its seat and
imagine the main pin to be at any one of the nine
numbered points of the first half of the wheel's revolu-
tion, turning forward, and then move the valve model
until its index points even with the mark at the corre-
sponding number of the scale that shows the different
positions of the combination lever; this will be the
cprrect location of the valve at that time, and the
relative positions of a point on the piston rod — say the
wrist pin — both pins in the union bar that connects
the lower end of the combination lever with the cross-
head, both ends of the radius rod, the reversing link,
its point of connection with the eccentric rod, and the
position of the eccentric are all shown by the same
numbers.
These diagrams are — with the exception of the
reduction in size — reproduced exactly from models
used by the Baldwin Locomotive Works, through the
courtesy of that company, and are quite interesting,
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THE WALSCHAERT VALVE GEAR 121
not only in telling the story of the operation of the
Walschaert valve gear, but also in settling to a certain
extent any questions as to differences that may be
thought to exist in the results obtained in the use of
valves of internal admission vs. external admission.
Theoretically, the Walschaert eccentric is placed
exactly 90 degrees of the wheel's circle from the main
crank-pin, and it has been referred to in this book,
in each instance, as so placed; but the diagrams,
Figs. 35 and 36, show the eccentric as further and
nearer to the main-pin than 90 degrees. This advance
or recession of the Walschaert eccentric from a right
angle to the main-pin is not for the purpose of securing
lead, as it is with the Stephenson motion; if the con-
nection of eccentric rod with the foot of the link was
on a horizontal line through the centre of the main
axle, then the eccentric would be set at just 90 degrees
from the main-pin; and it is endeavored to get the
eccentric rod to lie in as nearly a horizontal position
as possible when the main- pin is on the upper or lower
quarter, but this generally results in so great a length
of the lower extension or foot of the link — the distance
from link trunnion, or fulcrum, to the pin connecting
the link foot and eccentric rod — as to cause an over-
shortening of the throw of the link. So, there must
be a compromise; the foot of the link is not brought
down, usually, as low as theory would place it; its
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122 THE WALSCHAERT VALVE GEAR
connection with the eccentric rod is in most cases
above a horizontal line through the driving-wheel
hub centre, and to overcome the errors introduced
by the resultant angular position of the eccentric rod
the location of the eccentric in its relation toward the
main-pin is changed accordingly. In Fig. 35, repre-
senting an inside admission valve, it is seen that the
eccentric and main-pin are more than 90 degrees
apart, while with the outside admission valve of Fig.
36 the eccentric is less than a quarter turn from the
main-pin. The location of the eccentric as it is gov-
erned by the point of connection between the eccentric
rod and link is exemplified in Fig. 37.
Squaring the centres of axle and link f ulcrums, the
angle indicates the point of connection from the
eccentric rod to link foot with the link in a vertical
positibn and main- pin on a dead-centre; continuing,
the third side of the incomplete square furnishes the
radius upon which the eccentric shall be placed, and
it now depends upon which dead centre the main-pin
stands and whether the valve is of inside or outside
admission whether the eccentric shall be on one or the
other side of the axle; in Fig. 37 the valve is of outside
admission and the main-pin is on the back centre, so we
place the eccentric on the wheel radius that brings it
45 degrees nearer to the main-pin than 90 degrees
from it, because we find that a line from axle centre
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THE WALSCHAERT VALVE GEAR 123
to the point of connection of eccentric rod and link
foot is 45 degrees above the horizontal line through
the hub centre. In other words, the wheel radius on
CIS
s
O
.1
to
a
which the eccentric is placed must always be 90 degrees
from a Hne through the hub centre and link-foot pin
when the link is in an exactly vertical position — a
position in which the reverse lever can be moved
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124. THE WALSCHAERT VALVE GEAR
between the farthest go-ahead and back-up notches
on the quadrant without displacing the valve, and
with the main-pin on a dead-centre.
With outside admission valves the eccentric and
main-pin must be 90 degrees apart minus the number
of degrees represented by the elevation of the link-
foot pin above its normal position on the horizontal
line through the hub centre. With inside admission
valves, raising the link foot above the theoretically
normal position places the location of the eccentric 90
degrees plus the number of degrees that the link-foot
pin is raised, from the main-pin; thus, in Fig. 37 the
position is fehown in dotted lines in which the eccentric
would be placed if the valve was of inside admission
and the eccentric should follow the main-pin.
Fig. 37 represents an extreme case; but it would be
possible to raise the link until the line through the
hub centre and link-foot pin was perpendicular to the
horizontal line through hub centre; in that case, and
with outside admission valves, the eccentric would be
o degrees from the main- pin: That is, the main- pin
and eccentric would be on the same wheel radius.
With inside admission valves the eccentric would be
180 degrees from the main-pin, or, just opposite it. •
This supposititious case of extreme link elevation
most plainly illustrates why irregularities in the valve
motion are produced when the link-foot pin is raised
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THE WALSCHAERT VALVE GEAR 125
above the centre line of the axle; and the erratic
actions so introduced cannot be overcome. When
this connection from eccentric rod to link is normally
located, the rise and fall of the engine caused by the
alternate yielding and exertion of the driving-wheel
springs has no material effect on the motion delivered
to the valve, but when that point of connection is
raised above the normal, the interference to correct
action is in proportion to the distance the link-foot
pin is placed above the centre line of the axle. And
if we imagine a case in which this connection point is
raised to a position perpendicular to the axle centre,
it is plain that while the engine is running and rolling
from side to side over uneven track, for each inch
of rise or fall of the link support there will be a full
inch in the deflection of the connecting point between
the eccentric rod and link extension, and this deflection
will be in the direction of motion, causing alternate
quickening and halting in the valve's action.
Fig. 37 represents the half-way between the case of
extreme link elevation just considered and the techni-
cally correct position of the link in which the link-foot
pin is on the same level with the centre of the axle;
and while the former design would be practically
impossible in locomotive practice it would work very
well in stationary service. By reference to Fig. 37,
and bearing in mind that the distance between the
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126 THE WALSCHAERT VALVE GEAR
link fulcrum and axle centre is not invariable but
greater or less when the engine is running, it can be
understood why the link-foot pin should be as close to
its theoretically established location as possible; also,
why the eccentric in actual practice is not usually
exactly 90 degrees from the main pin. .
The folder diagrams. Figs. 35 and 36, show that by
being properly designed the Walschaert gear in con-
nection with piston valves of inside admission will
produce valve events corresponding closely to those
obtained from the use of the D-slide valve and outside
admission. It will be noted that the action is practically
identical in both cases, the steam admission taking
place at the point 7, and the exhaust closure occurring
and compression beginning at the point 8, with the
main-pin at the same point in its revolution in each
case.
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THIRD DIVISION
ADVANTAGES OF WALSCHAERT VALVE
GEAR
And Arguments for its Use as Against the Stephenson
Link Motion
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THIRD DIVISION
ADVANTAGES OF WALSCHAERT VALVE GEAR
And Arguments for its Use as against the Stephenson
Link Motion
(i) Accessibility. There is not room enough for
the Stephenson gear under a very large passenger
or freight locomotive. The eccentrics are crowded,
and proper inspection, not to speak of proper care,
is difficult, except over a pit. Valve gear to be properly
maintained must be accessible for inspection and
lubrication. The accessibility of Walschaert gear
should reduce engine failures.
(2) Weight, A saving of 1,745 pounds is possible
by using the Walschaert gear, in the case of a very
heavy passenger engine. The Stephenson gear, weigh-
ing as much as two tons, is far too heavy to be satis-
factorily reversed twice in every revolution on fast
running locomotives.
(3) Directness. Walschaert gear transmits the mov-
ing force to the valve in very nearly straight lines,
avoiding the springing and yielding of the rocker
arms, rocker shafts, and transmission bars, which
9
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I30 THE WALSCHAERT VALVE GEAR
cannot be avoided in these parts of the Stephenson
motion, even if they are made very heavy.
(4) Permanence 0} Adjustment, The advantage of
permanence of adjustment lies with the valve gear
which has no large eccentrics. This is proved by the
statement of. the Superintendent of Motive Power of
one of the great trunk lines — ^a comparative statement
covering the performances and condition of the valve
gear of engines that differ only in having Walschaert
vs. Stephenson gears. This statement appears in
this book later on. All connections in the Walschaert
gear are made with pins and bushings, which arc
designed specially to resist wear.
(5) Wear. Large eccentrics, besides occupying too
large space, wear unevenly, and lubrication is difficult
with the high surface velocities of the largest sizes.
With hardened pins and hardened bushings the Wal-
schaert gear has an important advantage in main-
tenance.
(6) Smooth Operation, Stephenson links, under the
influence of two eccentrics, move through wide angles,
resulting in a wedging action of the link-block, which
strains the gear when working hard, and produces
lost motion. Walschaert links oscillate through smaller
angles, producing less lost motion. The effect of this
angularity of the links is plainly discernible on the
testing plant.
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THE WALSCHAERT VALVE GEAR 131
(7) Frame Bracing. The removal of the valve
gear from between the driving wheels facilitates
bracing the frames of the locomotive laterally.
(8) Unvarying Advance of the Valve. Lead, if
present, is not altered by hooking-up the link.
(9) The General Adoption of Walschaert Gear
Throughout Continental Europe. Its use there for
over half a century.
As to accessibility, everything is in favor of the
Walschaert motion. The common Unk motion is
crowded in between the frames whiere it is very hard
to get at; the space that it occupies could well be
used for other purposes, and the valve gear requires too
much attention to be stowed away in a somewhat
inaccessible place. When break-downs occur on the
road, time is lost in doing repair work, or in disconnect-
ing, in the confined space inside the frame; and in the
shop, the locomotive with the Stephenson gear requires
considerably more time to have its valve gear set up
correctly than does the engine equipped with the
Walschaert motion. Imperfectly lubricated machinery
is expensive, and the oil used on railroads represents a
large sum annually. The double eccentrics require a
large amount of oil, but their location invites carelessness
in getting it properly applied, and the monthly strictures
against the men as to the amount used results in an
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132 THE WALSCHAERT VALVE GEAR
over-economy; the effect is that the eccentrics run
hot and trains are delayed. I was fireman on an
engine when an eccentric strap broke and a hole was
punched through the water leg of the firebox, not only
disabling our engine, but, through the complexity of
train operation, delaying and tying-up other trains
until the business of the whole division was disorgan-
ized. Oil was hard to get and hard to put on, else the
trouble would not have occurred, but it could not have
happened if our engine had been equipped with the
Walschaert gear.
No matter how conscientious the engineer may be,
it is a well-known fact that machinery placed where
it can be gotten at is taken better .care of, both as
regards oiling and inilpection, than where it is put in an
out-of-the way and crowded place.
It is not uncommon for the valves to get "dry" on
account of the lubricator choking, or becoming empty;
in such cases the tremendous resistance of the valve
under steam pressure throws increased labor upon the
eccentrics that would have but very little tendency to
over-heat the turned pin of the Walschaert gear; but
the location of the Stephenson eccentrics hides from
the engineman the first symptoms of trouble, and
afterward stands in the way of receiving proper relief.
The amount that the Walschaert gear saves in weight
over the common link motion is rather startling, being
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THE WALSCHAERT VALVE GEAR 133
in some cases very close to one-half. The motion,
from eccentric to valve, on a' big, modem passenger
engine is continually tearing itself to pieces. Is there
any wonder due, when one considers the weight of it
all, and that the joint action of two opposing eccentrics
are throwing the link and transmission mechanism
in one direction to be instantly stopped, started, thrown
the opposite way and stopped — only to be re-started
and stopped again — and so on with the rapidity
engendered by a speed of seventy or more miles an
hour? It is a wonder that eccentric straps, rods,
bolts, etc., stand the strain at all, and a weight of
metal must be there to give strength to the parts that
is one of the principal reasons for the adoption of the
Walschaert gear on so many* newly built engines;
the load has been lightened.
**It is understood that the Walschaert gear was
applied to the Lake Shore & Michigan Southern
Railway locomotives at the suggestion of The American
Locomotive Company, to whom belongs the credit
for the present tendency toward the introduction of
this gear in this country." — American Engineer and
Railroad Journal.
Now, therefore, as the above-named road has pur-
chased a great many new engines of various types,
r
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134 THE WALSCHAER'P VALVE GEAR
and as a number of those engines of each type has been
furnished with the Walschaert valve gear while the
others have the Stephenson link, it is possible to show
the figures regarding the weights, proportionately,
of the two gears, on engines that are in all other respects
exactly alike.
Following, in parallel column, are presented in detail
the weights of the several parts of the valve gears,
Stephenson and Walschaert, of the L. S. & M. S. — New
York Central, Class D, 2-8-0 freight engines, built by
the American Locomotive Company:
Stephenson. Walschaert.
lbs. lbs.
Crank pins, main 520 490
Crank-pin arms 100
Crosshead arms 60
Eccentric 600
Eccentric strap 800
Eccentric rods 200 220
Link 280 260
Link support . . .' 280
Link lifter 45
Reverse shaft and arms 260 400
Rockers 260
Rocker boxes 240
Transmission bar 300 140
Transmission-bar hanger .... 80 72
Valve rod 80 70
Vibrating rod ' 220
Vibrating link 70
Total, pounds 3,665 2,382
Saving in weight, pounds 11283
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THE WALSCHAERT VALVE GEAR 135
One thousand two hundred eighty-three pounds is
a tremendous weight to be included unnecessarily in
rapid-acting machinery; especially when the deflection
of one-thirty-second of an inch may change the motion
sufficiently to blind one of the events — lead, for in-
stance. And in substituting the Walschaert gear it
means cutting off thirty-five (35) per cent of the
weight of the old link motion.
But some of the above are fixed, immovable parts.
If we want to find the difference in weight of the
working parts we should cut out such as the reversing
shaft, rocker boxes, link support (Walschaert), etc.,
and we then find the weight of the Stephenson motion
gear to be 3,120 pounds, and that of the Walschaert
gear 1,702 pounds — a saving in weight of the parts
that thrust and take of 1,418 pounds, amounting to
the still more interesting figure of over forty-five (45)
per cent.
Of the heaviest passenger engines ever built, at this
date, — the class shown in Fig. 19 — some have Stephen-
son link, and some the Walschaert gear. The
comparative weights of the valve gears of this class,
J 2-6-2, are:
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136 THE WALSCHAERT VALVE GEAR
Stephenson. Walschaert.
lbs. lbs.
Crank pins, main 390 365
Crank-pin arms 80
Crosshead arms 50
Eccentric 740
Eccentric strap 880
Eccentric rods 200 175
Link 260 240
Link support 250
Link lifter , 120
Reverse shaft and arms 350 375
Rockers 280 325
Rocker boxes 300 300
Transmission bar 270 160
Transmission-bar hanger .... 120 65
Valve rod 1 30 100
Vibrating rod 180
Vibrating link 60
Total, pounds 4,040 2,725
Saving in weight, pounds i»3i5
or 32 i per cent.
Amount per cent saved in weight of the motion
parts of gear, nearly 47.
Another type of Classs J 2-6-2 carries the following
weights:
Stephenson. Walscharet.
lbs. lbs.
Crank pins, main 440 415
Crank-pin arms 90
Crosshead arms 50
Eccentric 740
Eccentric straps i ,1 20
Eccentric rods 280 200
Link ....,., , 300 275
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THE WALSCHAERT VALVE GEAR 137
Stephenson. Walschaert.
lbs. lbs.
Link support 260
Link lifter 120
Reverse shaft and arms 385 390
Rockers 280 350
Rocker boxes 300 325
Transmission bar 300 1 70
Transmission-bar hanger 120 75
Transmission-bar bracket ... 200
Valve rod 100 100
Vibrating rod 180
Vibrating link 60
Total, pounds 4.685 2,940
Saving in weight, pounds 1.745
Cutting out the non-moving pieces there is a diflFer-
ence in the weight of the working parts of the two gears
applied to Class J 2-6-2 — of this particular Prairie
type of engine — of 1,835 pounds, equalling a saving
by the use of the Walschaert valve gear of Forty-eight
plus per cent (48 + %). The motion part of the
latter gear, then, is but little more than one-half as
heavy as the corresponding part of the common link
motion used on other engines of the same class.
The energy consumed in keeping going all of the
superficial weight of the Stephenson valve gear on
our modern locomotives might just as well be expended
in carrying several more tons of train load. Its re-
ciprocating motion at high speeds is destructive. On
engines of large size the eccentrics are of such weight,
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138 THE WALSCHAERT VALVE GEAR
on account of their increased size made necessary by
the extraordinary diameter of the axles, that in spite
of an expensive amount of lubrication a braking
power is exerted, and they will run hot. These weights
of the valve gear make engines hard to reverse or
hook up, and there is a certain lack of economy when,
in spite of careful counterbalancing of the shifting
parts of the valve gear, any engine "handles" hard.
Freight engines run as fast as passenger engines do.
By that is meant that a freight engine has smaller
wheels, and to make the running time required of the
freight trains of to-day the smaller wheels of their
engines must make about as many revolutions per
minute as do the bigger wheels of the passenger engines
to make their time; and for this rapid action of the
machinery the lesser weight of the Walschaert gear
makes that type of valve motion most desirable. And
no change in locomotive design will call for any increase
in the number of reciprocating parts of the Walschaert
gear, thus saving the weights, and errors in the motion
due to vibration and lost travel that are present in
common with "transmission bars," etc.
This latter point is covered in the matter of directness.
There are but few motion parts to the Walschaert
gear, and they are of the same number for all engines
in all classes of service, except that sometimes the
connection from combination lever to valve-stem, or
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THE WALSCHAERT VALVE GEAR 139
from eccentric rod to link, has to be carried over by
a sort of rocker-arm arrangement on account of the
steam chest being rather far inside from the centre
Une of the cylinder.
A motive-power official will inform us that an engine
with the common link motion has a certain amount of
lead, in full gear, but he knows that that matter of
lead is decidedly uncertain — a variable quantity —
considering the interference of the numerous joints in
the gear from eccentric to valve, the slackness from
wear of the two eccentrics and. their encircling straps,
of the many pins and rockers and the vibration of the
transmission bar. And this lost motion is further
acted upon by the practice on many roads of using
piston valves of inside admission with closed "spools,"
instead of having the valves open from end to end;
at the instant of steam release from the cyUnder the
exhaust pressure acts directly against but one end of
the double piston, and with a power approximating
the steam pressure that is admitted to the low-pressure
cyUnder of a compound engine, forcibly closing in all
slackness of the motion from the valve clear back to
the eccentric.
In regard to permanence of adjustment, and the
effects of wear, the results obtained from the L. S. &
M. S. engine proves the superiority of the Walschaert
valve gear; the following statement is from the Super-
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I40 THE WALSCHAERT VALVE GEAR
intendent of Motive Power of that road, Mr. H. F.
BaU:
"In reference to the Walschaert valve gear, engine
No. 912 has now a total of iV inch lost motion in the
valves. This is the total lost motion in the whole mo-
tion work; the engine has made, approximately, 39,000
miles. Engine No. 5924 (with link motion), examined
the same date, had yw i^^h lost motion in the valve-
stem, and has made, approximately, 32,000 miles.
This seems to be very much in favor of the Walschaert
valve motion."
As to smoothness of operation, it is only necessary
to understand the construction of the Walschaert
gear and to compare it with the double eccentric
motion, or to watch it in action, to realize its niceness
of operation.
Removing the valve gear from between the frames
permits a cleared inside space for other uses that has
always been wished for. One of the common causes
of engine failures in recent years has been weak engine
frames, very often resulting in their breaking. At the
very point where strong cross-bracing is necessary —
between the cylinder casting and main driving-axle —
there has been no room for it, the space having been
taken up by the eccentric and link mechanism. With
the Walschaert gear, as much heavy frame bracing as
is desired may be put in — or anything else. There
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THE WALSCHAERT VALVE GEAR 141
are engines like that of the Erie motor car, previously
illustrated, where much inside space is needed for the
spring arrangement and main car-body bearing.
Some very heavy Atlantic type passenger engines
with the Stephenson Unk motion were received by a
certain road, and trouble that was experienced at
the start from hot driving-boxes never ceased. The
underneath construction of these engines compelled
placing the links in such a position that the eccentrics,
to be in line, were crowded outward, making necessary
the use of a too narrow driving-box, and a brass of
insufficient bearing surface for the great weight that
it had to support. The next delivery of engines to
that road were of the same class except that they had
the Walschaert valve gear, and wider driving-boxes
that had bearing surfaces proportionate to the weight
of the engine, and these engines ran cool from the first
trip. Nothing about the engine needs to be sacrificed
to make room for the Walschaert valve gear.
The improved design of the De Glehn Balanced
Compound has been adopted by the American Loco-
motive Company, and the Baldwin Locomotive Works,
in their Cole, and Vauclain, balanced compound
engines, respectively, and in each of which a crank-
axle is a principle feature. The manufacture of this
type of engine is increasing in America ^ince Europ)ean
practice has shown us the absence of danger from that
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142 THE WALSCHAERT VALVE GEAR
bugaboo — the crank-axle. Instead of crowding four
eccentrics and the rest of the valve motion — ^with its
heavy interference with perfect balance — among the
gear of the inside engines, it can be replaced, as with
the De Glehn engine, with the lighter, more accurate,
Walschaert gear on the outside of the frame and
wheels.
The possibilities that lie in the use of this valve gear
are not generally realized in this country; it can be
applied to engines of any type without material altera-
tion, and without the use of transmission mechanism.
The line of motion is nearly straight, and the longer
the eccentric rod and radius rod — the greater their
radius — the more perfect will be their work. Euro-
peans know these things; they seem to believe, also,
that the desired results from the use of this valve
motion are best secured in connection with the outside
admission, D-slide valve. On the main lines of
Continental Europe 90 per cent of the engines are
equipped with the Walschaert gear, and the remaining
10 per cent represents but a fraction of Stephenson
link motion. At the Lifege Exposition, out of 31 engines
on exhibition, 25 were fitted with the Walschaert
valve gear.
Its adaptabihty is great. If it is desirable, in order
to simplify the reversing mechanism on any particular
type of engine, to raise the radius rod and link-block
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THE WALSCHAERT VALVE GEAR 143
when the reverse lever is thrown forward, it will only
be necessary to change the position of the eccentric
180 degrees — from a quarter ahead of the main-pin,
with outside admission valves, to a quarter behind the
pin.
And now, as one of the chief peculiarities of the
Walschaert gear lies in the manner in which lead is
secured, and maintained unchanged throughout the
different points of cut-off, the general effects of lead are
worthy of speculation. Self -opinioned men, men who
think for themselves and are not too over-conservative,
are beginning to question if the advance of the valve,
any further than is necessary to' overcome the steam
lap, is really a help or a hindrance. If not a help,
can it fail to be a hindrance? There doesn't seem to
be any reason why, with any class of engine in any
branch of service, the amount of lead opening in
full gear should increase as the speed increases, as does
occur when the engine with the Stephenson Unk
motion is hooked up. With the Walschaert gear the
amount of lead suitable to the speed at which a par-
ticular engine will be expected to run or the work it
will be required to do can be decided upon and the
valve advanced to permit that opening, and that lead
remains positive, unaffected by hooking- up, and
almost entirely free from the shifting of results due to
lost motion and vibration.
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144 THE WALSCHAERT VALVE GEAR
An expert on valve motion has the following to say
in regard to this question; it is an extract from an article
in one of our leading technical journals:
" Opinion has grown, as error is apt to grow, that an
admission of steam is absolutely necessary to create a
cushion upon which the piston and connections may
gradually come to rest before beginning the return
stroke. Those who are accustomed with the nmning
of locomotives know that when the throttle valve is
closed the rods and reciprocating parts run smoothly,
even if loose. No pounding is observable at any rate
of speed.
*'ls it not reasonable to expect that the piston meet-
ing with steam resistance before it has completed its
stroke should rudely affect the bearings of the rods
and crank-pins, and induce an excess of friction?
It has been repeatedly shown that if the pre-admission
of steam amounts to a sufficient quantity to cause
compression, a marked increase in steam consumption
is shown.
" The real need is the readiness of admission of steam
at the time when it is required to move* the piston in
the other direction, and while the ordinary valve has
this advantage in a marked degree, this rapidity of
opening compensates in some degree for its other defects.
" Assuming, however, that lead is desirable for slightly
cushioning the piston while the working parts of the
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THE WALSCHAERT VALVE GEAR 145
engine are being subjected to intense friction, is it
not reasonable to assume that the same amount would
be sufficient for difiFerent rates of speed? Upon what
hypothesis can it be assumed that one-thirty-second
of an inch is sufficient opening at a moderate rate of
speed and that three-eighths of an inch is necessary
at a higher speed?"
Exactly; and if a small amount of lead is demanded
by those who think it necessary at certain times, the
use of the Walschaert gear will prevent that amount
from increasing as the speed increases and the reverse
lever is hooked up.
One night the writer was firing a little 4-4-0, 17-inch
by 24-inch engine pulling a very heavy passenger
train, when we broke down and had to disconnect
the engine on one side. After fixing things up in good
shape we proceeded; there was only one more stop to
be made short of our journey's end, but in spite of the
efforts of the engineer, we came to a standstill at that
station with the working engine on an exact dead
centre.
It was decided to unlock the Janney coupler behind
the tender, leaving the safety chains coupled, and
"pinch'' the engine ahead and off the dead centre,
and with the Janney set to couple, to pull the train a
few feet by the safety chains and allow the coupling
to "make" — trusting to luck to stop again with the
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146 THE WALSCHAERT VALVE GEAR
crank-pin ofiF the centre, in order to re-couple the air
hose.
The trainmen took turns operating the pinch-bar,
but their efforts were in vain. I noticed, however,
that just before their groans began to indicate the
application of cause toward hoped-for effect, the
engineer had opened the throttle-valve pretty strong.
The engine would not move, however, and the engineer
finally shut off steam, jumped down from the engine
and took the bar: "Now, Billy! Give 'er steam —
here she goes!" he promised; but she wouldn't move;
he kept on trying, with no better results, so I shut off
steam and opened the cylinder cocks.
The conductor had about decided to send for the
section men, when the engineer concluded to try
the pinch-bar again, and calling to me to open the
throttle, he threw himself at it once more: "Lay on,
Macduff!" thought I, with a sudden idea, and I did
not open the throttle valve this time; the result was
that the engine responded to the pinch-bar as promptly,
and was kept moving with as much ease as if it were
an empty flatcar.
That night, then and there, I lost all of my confidence
in the theory of lead. It was proven that lead not only
fails to be of any assistance in carrying an engine past
the dead centre but offers resistance to the crank-pin's
movement past the dead point. The force that lead
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THE WALSCHAERT VALVE GEAR 147
causes to be exerted when the engine is on a dead
centre absorbs, or nullifies, much of the energy fur-
nished by the other source of power at its zenith — the
engine on the other side, with its admission port wide
open and the relation of crank-pin to driving-axle
giving the maximum leverage.
If the pre-admission of steam to the cylinder, that
is referred to as lead, is finally conceded as necessary
only for cushioning the piston at the completion of its
stroke, any argument for it is now clearly fallacious,
for the reason that the exhaust may be cut off at any
point toward the finish of the piston's stroke and
the resultant compression will produce the cushioning
effect just as well — and more economically, — as evi-
denced by the quoted authority, than by means of any
pre-normal opening of the admission port.
Motive-power officials often try to induce engineers
to run their engines with full open throttle and reverse
lever hooked up to the limit, claiming that an engine
would run faster and work more economically that
way. That method has been tried, fairly, and also
the other one of using a lighter throttle and a little
longer travel of the valves, and invariably the latter
way gave the best results, both in speed and fuel
economy. It is not imagination, and might be attrib-
uted to the fact that the lower down the link is worked
the less the lead, with the Stephenson motion, and the
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148 THE WALSCHAERT VALVE GEAR
less "friction on the bearings of the rods and crank-
pins" there will be. Of course, it may be said in
answer, that there is but a slight increase in the amount
of lead from the point where the engineer worked the
lever up to the point at which the master mechanic
wanted it worked; yet there was a difference, and an
otherwise imexplained variance in the performances
of the* engine — ^favorable to the position of the reverse
lever in which it is claimed by some that the steam is
"wire-drawn."
The simplest test to prove the superiority of the
Walschaert valve gear, and the easiest to make, yet most
convincing to the practical mind, is, where there are
engines of the same general type except that some
are equipped with the Stephenson link and others have
the Walschaert gear, to note the boiler pressure re-
quired to move each of these engines from its stall
in the roundhouse, with its cylinders "cold." The
test with big "battleship" engines has shown that
eighty-five pounds on the steam gauge were required
to get the engine with the old link motion on the turn-
table, while the engine having the Walschaert valve
gear was moved out, easily, with the gauge showing
thirty-five pounds of steam.
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FOURTH DIVISION
QUESTIONS AND ANSWERS
Relating to the Walschaert Valve Gear
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FOURTH DIVISION
QUESTIONS AND ANSWERS
Relating to the Walschaert Valve Gear
Question i.— What is meant by "Valve Motion"?
Answer, — ^Valve motion, or valve gear, refers to the
system of rods, levers, etc., that transmits motion to
the main valve that is used to admit steam to, and
exhaust it from, the cylinder of an engine; it is the
action of the st^am in the cylinder that empowers the
piston.
Q. 2. — From where does the valve gear receive its
initial motion?
A. — ^The valve gear receives its motion from some
point, or points, in the machinery that is actuated by
the piston.
Q. 3. — What kind, or style, of valve is used in con-
nection with the Walschaert gear?
A. — ^Any valve that is used with any other form of
valve gear. Strictly speaking, the valve is not a part
' of the valve gear,
Q. 4. — ^What is the difference, then, between the
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152 THE WALSCHAERT VALVE GEAR
Walschaert gear and the Stephenson link motion so
generally used, until recently, in America?
A. — ^The difference is in the manner in which the
initial source of motion from the turning of the driving-
wheels is secured, in the way the gear is reversed to
change the direction in which the engine shall run,
and the method of securing lead.
Q. $• — Do not both the Stephenson and Walschaert
gears secure their initial motion through eccentrics
actuated by the turning of the main pair of driving-
wheels?
A. — ^Yes; the Stephenson link is given its motion
by two eccentrics keyed upon the main-axle, one of
which is thrown into gear to so actuate the valve that
the engine will run forward, while throwing the other
eccentric into gear will cause the engine to run back-
ward. In the Walschaert motion the Unk receives
the main, or initial, valve-actuating power through a
single eccentric, not on the axle but in the form of a
"return crank" fixed upon the main crank-pin, and
this eccentric is in full gear and works the link at its
full throw always, and with the engine running in either
direction.
Q. 6. — How is the Walschaert motion reversed?
• A. — ^The position of the radius rod that directly
actuates the valve-stem is shifted from one to the other
end of the link to cause reversion; the radius rod is
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THE WALSCHAERT VALVE GEAR 153
raised or lowered for this purpose by the regular re-
versing gear, the link being suspended from a bracket
by a fulcrum pin, or trunnion, at its exact centre.
Q. 7. — What is the position of the valve in relation
to the piston?
A. — Theoretically, the valve is always one-fourth of
a complete stroke, or cycle of motion, ahead of
the piston, when the engine is running in eith^
direction.
Q. 8.— What is meant by Lead ?
A. — If the valve was exactly one-fourth of a cycle of
motion in advance of the piston, the eccentric that
actuates it would necessarily be placed at a point on
the axle just 90 degrees ahead of the main crank-pin
in respect to the direction in which that eccentric should
cause the engine to run, but, if so placed, when the
piston was at the beginning of its stroke — at one end
of the cylinder — the valve would be exactly centred
on its seat, with both ports, or steam passages, to the
cyUnder covered and closed. In actual practice the
valve is advanced slightly, but far enough, in the
direction of its required travel, to open, by a very
short distance, the admission port at the piston end
of the cylinder; this gives a pre-admission of steam
against the piston just before its stroke has been com-
pleted, and has the double effect of cushioning the
piston and hastening the full opening of the steam
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154 THE WALSCHAERT VALVk GEAR
admission port. This preliminary port opening to the
cylinder is termed the Lead.
Q. 9. — What further effects afe produced in ad-
'vancing th6 valve to create th^ lead opening, that
cannot be regarded as beneficial?
A. — The advance of the valve causes an earlier
closing of the exhaust of the used steam from the
cylinder, thereby creating higher compression ahead
of the piston — ^between the piston and the cylinder
head toward which it is travellihg; the cut-off of live
steam that is being admitted to the cylinder occurs
sooner during the piston's stroke, and this detracts
from the turning power of the main crank when the
engine is working in full gear with a heavy load; atfd,
as giving lead hastens all of the valve events, the steam
that is driving the piston is retained in the cylinder
during a shorter part of its stroke, and this earlier
steam release is a loss of a certain per cent of the
steam's expansive force.
Q. 10. — After the cut-off of the ezhiEtust has oc^
curred, will not the compression between the j^istoA
and cylinder head provide the cushioning effect that
may be necessary as the working parts approach the
reversing point in their motion?
A.— Yes, the very slight amount of compressible
resistance that is deemed necessary may be so obtained,
by a suitable design of valve motion.
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THE WALSCHAERT VALVE GEAR 155
Q. II. — How is the advance of the valve to create
lead opening secured with the Stephenson link mo-
tion?
A. — By advancing both the "go-ahead" and the
"back-up" eccentrics in the proper directions, on the
axle.
Q. 12. — How is lead obtained with the Walschaert
gear?
A. — In the Walschaert valve gear lead is obtained
from the straight-line motion of the piston^ instead of
from the circular motion of the axle with its errors
incidental to the angularity of the conveying rods.
Walschaert's vertical combination, lever has its lower
end connected to the crosshead and the upper end
to the valve-stem where an outside admission valve
is used; intermediately, the radius-rod connection
with the combination • lever forms its fulcrum, and
the motion derived from the crosshead so modifies the
motion imparted by the single eccentric, through the
radius rod, as to produce the required lead in either
forward or back gear. With the use of inside admission
valves the points of connection of the radius rod and
valve-stem to the combination lever are reversed, the
radius rod being connected to the extreme upper end
of the lever and the valve-stem connected intermediately.
Q. 13. — Does the lead, as derived by the Stephenson
method, remain constant?
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156 THE WALSCHAERT VALVE GEAR
A. — No; each eccentric is separately adjusted, or
advanced, to give the decided amount of lead when in
full gear, but as the link is hooked up the lead auto-
matically increases.
Q. 14. — Is this increase of lead to be desired?
A. — It is not, in any class of service.
Q. 15.— Does the lead vary with the Walschaert
gear?
A. — No; with the Walschaert method lead, if
present, remains unvarjungly the same at all points
of the cut-off.
Q. 16. — Is the position of the valve advanced for
any other purpose than that of securing lead?
A. — ^Yes. The steam edges of the valve are widened
beyond the outside edges of the admission ports,, and
the first advance of the valve is for the purpose of
overcoming the delay of port opening in consequence of
this overlap. The distance the edges of the valve
extend beyond the port openings is termed the lap,
and the valve must be moved far enough to overcome
the lap before the opening for lead can begin.
Q. 17. — Is the further advance of the valve to secure
lead necessary?
A. — ^Whether lead is a necessity or not is a matter of
argument, but it is being conceded by many expert
men that lead, as a port opening, is not necessary,
and by some it is considered a detriment.
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THE WALSCHAERT VALVE GEAR 157
Q. 18. — Explain the maimer in which lead is de-
rived through the action of the Walschaert combi-
nation lever.
A. — ^The Walschaert eccentric is set exactly 90
degrees, in effect, from the main crank-pin, and if the
combination lever were not present the valve would
always be a "quarter" from the piston, and would be
centred on the seat with both admission ports covered
when the piston was at either end of the' cylinder.
Now we introduce the combination lever: The con-
nection of radius rod near, or at, the upper end of the
combination lever represents its fulcrum; the lower
end of the lever is connected with the crosshead which
is now at one end of its travel in the guides. Now,
if the valve-stem is connected to the combination lever
above the fulcrum (radius-rod connection) it is plain
that the angle of the short (upper) end of the com-
bination lever will throw the valve, slightly, in a direc-
tion opposite to the position of the piston in the cylinder,
and this is the correct movement to be given the valve
with outside admission to secure the port opening for
lead. If, however, the valve-stem is connected to
the combination lever below the fulcrum, or radius-
rod pin, the valve will be draimi in the direction 0} the
piston^s position in the cylinder by the angle of the
short end of the combination lever, and this is the
proper direction for the valve of inside admission to
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IS8 THE WALSCHAERT VALVE GEAR
be advanced in order to permit the pre-admission of
steam against the piston, called lead.
Q. 19. — Suppose that an engine should be designed
to use the Walschaert valve gear, and lead was not
desired : That is, with the crank-pin on a dead centre
and piston at an end of its stroke the admission port
would not be open any, — steam edges of the valve
and port line-and-line — are we to infer that the com-
bination lever would not be necessary— that it could
be dispensed with?
A. — Not at all. The combination lever must be
included in the Walschaert gear on any engine and
with any style of valve. As explained, an advance of
the valve is necessary to move it the distance of the
lap, so that the steam edge of the valve and the out-
side edge of the admission port will be line-and-line
when the piston is at the start of its stroke and lead
not required. The amount of advance of the valve
derived from the action of the combination lever is
equal to the distance 0} lap, or lap plus lead, according
as the design of the engine calls for.
Q. 20. — Is there not a great deal of confusion as to
the actual meaning of lead?
A. — ^Yes. The angular advance of the Stephenson
eccentric upon the axle and the angular inclination of
the Walschaert combination lever are often referred
to as the lead, because it is known that they cause an
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THE WALSCHAERT VALVE GEAR 159
advanced motion of the valve, when, as just shown,,
an advance of the valve is highly necessary even
although it gives no actual lead.
Q. 21. — Assuming an engine to be running forward,
is the Walschaert eccentric placed a quarter ahead,
or a quarter behind, the main crank-^pin?
A. — ^Thisis a variable matter, depending upon the
construction of the reversing gear; if, with the reverse
lever in the forward gear the radius rod is worked by.
the lower end of the link, with outside admission valves
the eccentric is placed a quarter ahead of the main-pin
and with valves of inside admission the eccentric is
just opposite, or a quarter behind the main crank-pin.
Q. 22.— Is the Walschaert valve gear of the type
referred to as of " direct motion " ?
A. — ^The Walschaert motion is either direct or in-,
direct, according as t6 which direction the engine is
running. When the radius rod is working below the
centre, or fulcrum, of the Unk there is a single direction
of motion from the eccentric to . the valve and the
motion is direct; but with the radius rod working
above the centre of the link, the motion is indirect,
for the reason that the link then acts as a double
rocker-arm, and when the eccentric throws the lower
end of the link in one direction the upper end of the
link moves the valve the opposite way.
Q. 23. — Reversing the engine, then, changes the
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i6o THE WALSCHAERT VALVE GEAR
motion from direct to indirect, and vice versa, does it
not?
A.— Yes.
Q. 24. — ^The answers to Questions 13 and others,
refer to shorter cut-off and '< hooking-up " the link:
What is meant by those terms?
A. — Together, those terms represent cause and
effect; hooking-up is the cause and shorter cut-off is
the effect. Referring to the Waischaert gear, when
the radius rod is working in either extreme end of
the Unk, it is giving the valve its longest travel and
steam is being admitted to the cylinder with the maxi-
mum limit of port opening; hooking-up really means
drawing the reverse lever from a full-gear, comer
notch of its quadrant to a notch farther up, nearer the
centre, and this hooking-up of the reverse lever draws
the radius rod to a point nearer the centre of the
hnk, with the result that the motion of the radius rod
is reduced and it, in turn, by its shortened travel
shortens the whole travel of the valve; the effect of
this is that the admission port is closed earUer during
the stroke of the piston, and the expansive force of
the steam is utilized to drive the piston during the re-
mainder of the stroke. The closing of the admission
port is referred to as the cut-off, and therefore this
earlier closing of the port is termed shorter cut-ofi.
Q. 2$. — When the reverse lever has been hoojked up
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THE WALSCHAERT VALVE GEAR i6i
to the centre notch of its quadrant how much travel
will the radius rod give to the valve?
A. — ^None. When the reverse .lever is in the centre
notch the link-block (to which the radius rod is attached)
is exactly centred in the link — its pin centred exactly
with the fulcrum pin of^ the Unk — and the Unk can
impart no motion to the radius rod. The valve will
have a short niotion at this time, however, the motion
produced by the combination lever, and its full travel
with the reverse lever on the centre will be just twice
the distance of lap plus lead.
Q. 26. — With the reverse lever in forward gear the
radius rod is carried at the lower end of the link,
and in back gear at the upper end of the link, is
it not?
A. — ^Yes, this is American practice, but it can be
arranged otherwise, if more convenient, and will make
unnecessary the multiplicity of levers in the reversing
gear that is sometimes seen where the above arrange-
ment is adhered to. The radius rod may be carried
in the upper end of the link to make the engine run
forward and at the lower end to run backward, and in
such case it is only necessary, for further change, to
move the position of the eccentric 180 degrees — from
a quarter ahead to a quarter behind the main pin, or
vice versa.
Q, 27. — Is it easier to secure equal cut-off at both
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i62 THE WALSCHAERT VALVE GEAR
ends of the cylinder with the Walschaert gear than
with the Stephenson link motion?
A. — ^Yes. The Walschaert motion is more simple
and direct, and through the regular action of the link
and combination lever the cut-ofiF is maintained equal
at both ends of the cylinder, in either gear and with
the reverse lever hooked up to any notch in the quadrant.
Q. 28. — Why is the Walschaert link curved in an
opposite way to the curve of the Stephenson link, and
what is the radius of the curve of the link?
A. — ^The radius of curve of the Walschaert link is
equal to the length of the radius rod, and the reason
for this and the reason for the link curving in the
direction it does, is, that as the radius rod is raised or
lowered to shorten or lengthen the cut-off, the valve
will not be erroneously affected. The theory of this
is nicely exemplified by setting the engine on either
dead centre, when the reverse lever may be moved
from one comer notch to the other extreme end of the
quadrant without changing the position of the valve,
the link-block having the same curve to its path as the
curve of the link.
Q. 29. — Is it possible to make any changes in the
adjustment of the Walschaert gear on the road, or
any such roundhouse experiments as are often made
with the common link motion?
A. — It is not; sometimes, however, a slight irregular-
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THE WALSCHAERT VALVE GEAR 163
ity in the motion may be corrected by lengthening or
shortening the eccentric rod, only, but even this is
usually a " back shop" job.
Q. 30. — Is it not possible for the length of the ec-
centric rod to become slightly changed?
A. — Only as it may through a change in the ad-
justment of the bearings at the back-end connection
to the eccentric crank; such change may have been
made intentionally, or may be due to service conditions.
Q. 31. — Can any other part of the Walschaert gear,
except the eccentric rod, be changed or adjusted, out-
side of the machine shop?
A. — ^No. Neither is it ever necessary, and as the
lost motion from wear is hardly perceptible after many
months of service an engine may be run for a longer
time between shopping.
Q. 32. — Does any part of the Walschaert gear have
a tendency toward heating?
A. — ^The Walschaert valve gear is peculiarly free
from any incUnation to heat, except that occasionally
the gear is not properly designed to meet unusual
conditions of track and service, and eccentric rod
pins will heat from the twisting effect between the
driving-wheels and engine frame. This, however, is
not a constitutional disorder, and may be cured, or
prevented.
Q. 33- — In order to insure correct action of the
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i64 THE WALSCHAERT VALVE GEAR
Walschaert valve gear what parts of the engine out-
side of the valve gear should be kept up in good con-
dition, and as free as possible from lost motion?
A. — No form of valve motion will show good results
if the other working parts in general of the engine are
not kept up, but in particular, the driving-boxes should
not sustain lost motion.
Q. 34. — Is it a fact that lost motion in the driving-
boxes induces greater error in the motion of the valve
with the Walschaert gear than with the Stephenson
link motion?
A. — Such is not the fact, whatever; although the
Walschaert eccentric is a greater distance from the
centre of the driving-box, usually, than the eccentrics
on the axle are, and any lost motion between the
driving-box and engine frame will have a slightly
greater effect at the Walschaert eccentric pin than it
would have at the link-motion eccentrics on the axle;
yet, with the Stephenson eccentrics the full amount of
this lost motion is delivered to the valve with the
link working in full gear; while. in the Walschaert mo-
tion the amount of the variation is greatly, decreased
through the long leverage of the link foot.
Q. 35. — Does the up-and-down motion of the en-
gine on its springs affect the steam distribution of
the Stephenson link motion?
A. — 'Ves,i to a* very noticeable extent.
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THE WALSCHAERT VALVE GEAR 165
Q. 36. — Does this motion of the engine have an
equal disturbing effect on the valve's motion with the
Walschaert gear?
A. — ^No, it has no effect, unless the connection of
eccentric rod to link foot is placed at too high a point
above the centre line of the axle.
Q. 37. — When the crosshead is at the exact centre
of its travel,, main-pin on the upper or lower working
quarter, reverse lever in centre notch, and the com-
bination lever in a plumb vertical position, at what
point in its travel should the valve be standing?
A. — ^The valve at this time should be perfectly
central on its seat, with both admission ports covered.
Q. 38. — What is meant by the above expression of
the main-pin being on the '^ working quarter '' ?
A. — ^When the main-pin is on the actual quarter —
either the upper or lower — it is on a perpendicular
line through the centre of the axle, but the piston will
not be in the exact centre of the cylinder, owing to the
angularity of the main rod. On the other hand, if the
piston is at the true centre of the cylinder — as was
supposed in the foregoing question — the main-pin
will be a slight distance away from the perpendicular
line through the centre of the wheel, or axle, but it
is now on the working quarter because, technically,
it has half completed a single stroke; if the back end
of the main rod should now be disconnected from the
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i66 THE WALSCHAERT VALVE GEAR
main-pin and dropped, or raised, as the case demands,
until it was on a horizontal line, the opening for the
main-pin in the stub-end of the main rod would centre,
exactly, over the centre of the wheel hub, proving that
it was half-way in its, stroke. The longer the main
rod the less its angularity and the lesser will be the
difference between the actual and the working quarter-
positions of the main-pin.
Q. 39. — The engine standing with piston at the true
centre of the cylinder on one side and the reverse lever
in the middle notch of the quadrant, suppose that the
valve was not exactly centred — opening the throttle
would cause steam to blow from one of the cylinder
cocks on that side of the engine : What could be the
cause, and how remedy it ?
A. — First, be sure that the reverse lever is in the
middle notch; a mistake may have been made in
laying out the notches of the quadrant, or in setting it
up; when the link-block pin and the link-fulcrum pin
are centred together the reverse lever is in the proper
middle notch, and when they are so situated and the
valve is not covering the admission ports completely
with piston in exact centre of the cylinder, undoubtedly
the Unk bearer, which is attached, commonly, to the
guides, varies a little in its position, either fore or aft,
and should be moved enough to correct the error; or
the valve-stem can be lengthened or shortened, but as
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THE WALSCKAERT VALVE GEAR 167
this induces other minor errors the other method would
be preferable.
Q. 40. — Would not moving the position of the ful-
crum that carries the link produce other error in
shifting the distance between it and the eccentric?
A. — Re-setting the link fulcrum might correct the
whole motion, if it had been set up untrue; but if
correcting the position of the link fulcrum should
cause the error suggested, that, again, can be corrected
by adjusting the length of the eccentric rod. Here is
a fundamental point to remember: The gear from the
link forward, inclusive, is permanently set up, all
motion bearers being in rigid attachment to the guides.
Back of the link, however, there may be changes in
distances due to wear and consequent lost motion, and
for that reason the eccentric rod, alone, may be length-
ened or shortened as may be found necessary.
Q. 41. — On the big, modem engines that are being
equipped with the Walschaert valve gear there does
not seem to be any convenient way of changing the
length of the eccentric rod except in the adjustment
of the bearings at its back end; how, then, could the
length be altered as advised?
A. — Outside of the method just referred to, as stated
before, it is a "back shop" job to alter the length of
the eccentric rod, and there is where it should be done.
The earlier built engines, with much lighter rods, and
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i68 THE WAISCHAERT VALVE GEAR
foreign locomotives of the present date, had, and have,
adjustable eccentric rods. In Fig. lo, Wm. Mason's
improved design of the Walschaert gear, the eccentric
rod is shown to have adjusting nuts near the con-
nection to the link foot.
Q. 42. — Then, if the eccentric rod is the only part of
the Walschaert valve gear that can be changed out-
side of the machine shop and the only part that should
be altered at any time in the shop, this motion is not
likely to be tampered with, nor to get ''out of
square ** ?
A. — ^That is right. The Walschaert valve gear will
not wear away in its bearing parts enough to make it
necessary to have adjusting devices.
Q. 43. — Explain when it will be necessary to correct
the length of the eccentric rod.
A. — Set the engine with the main crank-pin on the
forward dead centre on one side, and have the reverse
lever moved from the go-ahead corner notch up
toward the centre of the quadrant; while the link-block
is rising, if the valve-stem is pushed forward slightly
the eccentric rod should be lengthened; but if the
valve-stem should be drawn backward by the rise of
the link-block the eccentric rod needs to be shortened.
In either case make but slight changes in the length
of the rod, and keep on testing until hooking up the
lever to the centre has no effect on the valve-stem nor
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THE WALSCHAERT VALV^ GEAR 169
radius rod. Then test, and alter if necessary, the
other side in the same way, but with the main pin on
the hack dead centre.
Q. 44. — The numerous engravings of locomotives
equipped with the Walschaert valve gear show that
the link bracket is invariably attached to the guide-
bearer, or yoke, and the slide for the valve-stem is
mounted on the upper guide-bar: Does this just
happen so, and as a matter of cbnveniencei or is
there a reason why the main supports of the Wal-
schaert gear should always be so contained?
A. — It is very important that the trunnion upon
which the link oscillates should be fixed at an unvary-
ing distance from the cylinder, and for assurance that
the distance will be permanently maintained, the
link bracket should be rigidly fastened to the guides;
and as the valve-stem slide supports the combination
lever and front end of the radius rod, it represents a
point where no variation in the motion is permissible,
and it, too, is secured fixedly to the guides.
A type of heavy-freight engine has recently been
built on which it would have been inconvenient to
hang the link as recommended, and a large, hollow,
cast-steel bracket was laid across, joining the bars of
the engine frame on both sides just back of the guide-
yoke, to act both as a frame binder and brace and a
carrier for the link bracket. With one class of .this
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I70 THE WALSCHAERT VALVE GEAR
general type the big shell casting is bolted to the guide
yoke as well as the frame, and becomes a most sub-
stantia engine frame and valve-gear stiflFener, but
with another class of engines the casting referred to is
separate from the guides yet carries the link, and as
the American bar-frame is not altogether unyielding,
this big, powerful freight engine will in time, no doubt,
develop certain irregularities in the valve's action
that may be attributed by some to the fact that the
engine is equipped with the Walschaert valve gear.
Q. 45. — If an engine breaks any part of the ma-
chinery while on the road, is there any great differ-
ence in the method of disconnecting the disabled side
and setting things right so as to proceed, as to whether
the valve gear is of the Walschaert type or the Stephen-
son link motion?
A. — ^Yes; and if the break occurs within the valve
gear the diflference in time consumed in making the
temporary repairs necessary to get the engine moving
under its own steam is so greatly in favor of the Wal-
schaert as to be one of the good reasons for its adop-
tion, because it means less time lost in delays to the rail-
road's one source of revenue — the turning wheels.
When railway motive power was not so large and
heavy as at present, and any part of the machinery
on one side of an engine was broken so as to disable
that side, it was the rule to take down the main rod
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THE WALSCHAERT VALVE GEAR 171
and block the valve after disconnecting the valve-stem;
the main rod had to come down from one side, always,
when the engine was only able to work steam on the
other side. The piston was then held at the back end
of the cylinder by blocking the crosshead, and the
valve on that side was set so as to cover both steam
ports by blocking it or clamping the valve-stem; not
a great deal of knowledge or ingenuity was required;
simply follow the custom.
Now, however, the enormous weight of the main
rod generally prohibits taking it down on the road;
leaving it up in place suggests that the piston will
"drift" in the cylinder while the engine is running
dead on that side, and that the crosshead will impart
motion to the combination lever, et al. So that a
few questions asked and answered on the subject, of
common breakdowns and the accidents that might
happen to the parts of the Walschaert valve gear
would be appropriate. ,
Q. 46. — In discussing the subject of breakdowns and
the methods of procedure in consequence, '^ blocking
the valve" will be mentioned several times; what is
meant by that expression, and when and how should
it be done?
A. — ^When any part of the valve gear is disabled on
one side of the engine so that the valve will not receive
its correct motion, or if any other part of the machinery
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172 THE WALSCHAERT VALVE GEAR
on that side of the engme is in such a dainaged con-
dition that steam must not be delivered to the cylinder
of that side while the engine is working on the other
side, the gear must be disconnected so far on the
disabled side that the valve "shall not be disturbed,
after which the valve must be placed in a central
position on its seat, by moving the valve-stem, whereby
both admission ports to the cylinder are covered.
After the valve has been correctly centred, if the
throttle is slightly opened no steam will blow from the
opened cylinder cocks on the disabled side . of the
engine. The cylinder cock rigging should then be
disconnected on the damaged side of the engine, so
that they could be set permanently open while the
engineer opened or closed the cocks on the other side
without interference; one reason for doing this is that if
the valve should get moved far enough to start uncov-
ering one of the admission ports steam would blow
from the cylinder cock at that end of the cylinder and
announce the shift of the valve when the throttle was
opened.
On many roads a clamp is furnished and carried on
every engine, by which the valve-stem can be secured
immovably in a position that places the valve squarely
over the ports. When such clamp was not at hand,
it was formerly the rule, with a D-slide valve, to raise
the steam chest cover and place retaining blocks
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THE WALSCHAERT VALVE GEAR 173
ahead and back of the valve; but it is almost an
impossible task to raise the steam chest cover on one
of our big, modem engines, and it is not at all unsafe
to neglect the inside blocking; just centre the valve,
and when steam is used it will put such a great weight
upon the valve that its f rictional resistance will cause ,
it to adhere to the seat beyond any danger of its moving,
unless the engine receives a hard bump as in switching
or coupling to cars, and in that case the engineer will
quickly discover the fact from seeing the steam at one
of the cylinder cocks.
Inside admission piston valves are so perfectly
balanced — fore and aft — that one need not hesitate
to trust them to "stay put" without clamping; still,
if there is a clamp provided, use it.
Some engineers with a high reputation for keeping the
wheels turning in spite of mishaps, refuse to block
the valve on the disabled side of the engine and they
leave the main rod up, also; it is out of the question
to take down, on the road, the heavy main rod that we
now find on most engines, and if the engine subse-
quently stops with the live side on the dead centre,
the disconnected valve can be temporarily moved far
enough to open the desired steam port and enough
steam then used to start the engine and get the work-
ing side off the centre; the air brake can then be
applied to stop the engine with the live side off the
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174 THE WALSCHAERT VALVE GEAR
centre, and with the throttle closed the disconnected
valve is again put on centre, and the train proceeds.
When the main rod is left up, the fixed-open cylinder
cocks will generally give relief ejiough to prevent
compression and vacuum* in the cylinder as the piston
chums forth and back, but for further relief some
engineers always unscrew the cylinder cocks to provide
an increased opening in each end of the cylinder. If
•the cylinder has by-pass valves they can be made to
take care of the churning of the piston. The piston
will run dry, however, and needs lubrication; oil
must be introduced to the cylinder if the engine is to
be run for any considerable distance. The lubricator
may be allowed to feed oil to the steam chest on the
broken-down side about the same as usual,' and at
certain stops along the road the valve can be moved
by the valve-stem — if not blocked — enough to open
one, or each alternately, of the admission ports and
given a little steam, the oil collected in the steam chest
will be blown down into the cylinder.
Q. 47. — If a side rod breaks, or should otherwise
be removed from the engine equipped with the Wal-
schaert valve gear, and no other damage results to the
machinery, could it have the effect of totally disabling
the engine?
A. — ^No. The engine would still work all right on
the uninjured side in all such cases.
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THE WALSCHAERT VALVE GEAR 175
Q. 48. — Could the breaking of a side rod totally
disable an engine with the Stephenson link motion?
A. — Yes, on certain types of engines where the
eccentrics are attached to other than the main-axle —
and this is quite common on engines with three or
more pairs of driving-wheels — if a side rod connecting
the main pair of driving-wheels with the pair that
mounts the eccentric axle should break, tMe same
section of side rod on the other side ot the engine should
be taken down, and this would render the valve motion
inoperative. With the Walschaert gear the eccentric
is always on the main pair of wheels, and therefore is
unaflFected by any damage to side rods.
Q. 49. — In cases requiring the valve to be blocked,
the valve-stem should, of course, first be disconnected,
or at least disconnection made at some point between
the valve and the regular source of its motion, and
with the Stephenson link motion the valve-stem is the
most convenient place : Is it, with the Walschaert
gear?
A. — ^No; it is practically out of the question to dis-
connect the valve-stem itself on most engines having
the Walschaert gear, as it usually has a crosshead
working in a guide and there is no place between the
crosshead and the packing gland for its separation,
.but the same effect is produced by disconnecting the
radius rod.
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176 THE WALSCHAERT VALVE GEAR
Q. so.— If disconnection of the radius rod in the
Walschaert gear has the same effect as disconnecting
the valve-stem of the common link motion, then the
radius rod will have to come down whenever the en-
gine is so disabled on one side that the valve must be
blocked; so you will explain in detail how one should
go about it.
A. — ^The radius rod need not be taken down in all
such cases of disability, but will always have to be, at
least, disconnected.
Remove the pin from the joint of radius rod and
combination lever and raise the disconnected end of
the radius rod just above any chance of interference
with the combination lever, suspending the rod by
strong wiring or rope of such length as to permit it to
swing freely to the motion of the link, taking par-
ticular care that the suspended end of the radius rod
will not strike anything else. This method should only
be resorted to, however, when the engine has only a
short distance to go to reach its terminal and can be
run at a moderate Speed, only. In answer to subse-
quent questions on breakdowns the following instruc-
tions for disconnecting the radius rod should be ob-
served:
If the engine is to be run any considerable distance,
or may be speeded up at times, with one side disabled,
a safer and more commendable method is, first, place
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THE WALSCHAERT VALVE GEAR 177
the reverse lever in the centre notch of the quadrant in
order to get the back end of the radius rod and the
Unk-block in the exact centre of the link; then saw
a couple of pieces of wood to fit, and insert them
between the bottom of the Unk and the link-block, and
secure them in position in order to support the back
end of the radius rod at the centre of the link; now
disconnect the hanger between lifting arm and radius
rod and take out the pin from the front end of the
latter at its connection with the combination lever,
wiring the radius rod up, as previously directed, or
suspending it by anything that will support its weight,
as there will be no motion imparted to it now. After
centering the valve, and blocking it or clamping the
valve-stem — or trusting that the pressure of the steam
will hold it in its central position — ^itwill not be necessary
to do anything with the combination lever, as the motion
imparted to its lower end will not be likely to affect
the valve, e\en if not clampeu; but, — after disconnect-
ing the radius rod from the combination lever, always
watch the first movement of the crosshead to see that
the combination lever does not strike the wrist-pin —
the pin by which the front end of the main rod is
connected to the crosshead — as the motion of the lever
is altered by the disconnection and pause of its upper
end. Blocks of the proper size to hold the radius rod
in the centre of the link, and with their upper ends
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178 THE WALSCHAERT VALVE GEAR
shaped half-round, should be carried on all engines
equipped with the Walschaert valve gear.*
Q. Si.— What should be done in case of a broken
radius rod?
A. — ^The best plan is to take down all of the pieces
of the broken rod, disconnecting them from the com-
bination lever, suspension bar, or hanger, and link-
block; but if there is very much left of the rod forward
of the link, it can be blocked up in the centre of the*
link, disconnected from the suspension bjar, and its
front end wired or tied up as before mentioned, and
the valve centred and secured.
Q. $2. — When the suspension bar, or hanger, is
connected to an extension of the radius rod back of
the link, and that back extension of the rod should
get broken ofF, or the suspension bar or lifting arm
should break, what should you do?
A. — ^These troubles should be treated about alike.
If the engine is to run forward, place a short block
in the link under the radius rod or the link-block, so
that the forward section of the radius rod will be held
at about the same position in the link as the one on the
* The construction of the Walschaert link is a little differ-
ent in detail as designed by the different locomotive builders,
and the shape of the blocks to be used in the link when it
is desired to carry the radius rod and link-block without
motion, varies enough that it would not be practicable to
illustrate a pattern.
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THE WALSCHAERT VALVE GEAR 179
other side when the reverse lever is in the notch that
it will be expected to work in. An average should
be struck in regard to this, as the reverse lever should
neither be hooked up any further, after the positions
of the radius rods have been matched, nor dropped a
notch lower. Of course, the broken parts should be
detached, and another block placed in the link above
the link-block or radius rod to prevent their slipping up.
Q. 53. — An eccentric rod seldom breaks with the
Walschaert gear, while it is not uncommon in the
Stephenson link motion; if, howeyer, the Walschaert
eccentric rod should break, what then should be done?
A. — ^After removing the broken parts of a Walschaert
eccentric rod throw the reverse lever to the forward
corner notch in order to lower the radius rod and block
to the bottom of the link; then disconnect the sus-
pension bar from the radius rod, and the radius rod
from the combination lever; raise the front end of
the radius rod above interference, and, wiring through
the pin hole, attach its forward end firmly and im-
movably to anything convenient and soUd in order to
k^ep the link from rotating, as with the eccentric rod
detached there will be nothing but the radius rod to
keep it steadied. Block the valve, etc., in the manner
heretofore described, and proceed.
Q. 54. — If the valve-stem^hould break what course
should you pursue?
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i8o THE WALSCHAERT VALVE GEAR
A. — Disconnect the radius rod in the recommended
manner and centre the valve, blocking or clamping
the valve in this case if it Were possible, and leave the
combination lever in place, providing that as the lower
end swings forth and back it does not strike the pro-
jection of the pin that connects the main rod to the
crosshead, for its motion will be somewhat changed
since there is no action of the slide at its upper end;
this slide — ^from which the valve-stem has been dis-
connected by breakage — may be placed at any position
on the sUde bar that will provide a safer swing to the
combination lever, and should he blocked in that posi-
tion so that the motion of the lower end of the combi-
nation lever could not induce a movement of its upper
end that would result in the valve being pushed off centre.
Q. 55. — If the long (lower) section of the combi-
nation lever or its connecting link to the crosshead,
should get broken, what should be done? *
A. — ^Detach the pieces of the link bar, or the broken-
off, lower piece of the combination lever; disconnect
the radius rod as explained before, and centre the
valve. The remaining stub of the combination lever
must be drawn out of the way, forward or back, so
that it will not be struck by the pin in the crosshead
to which the main rod is connected, when the main rod
is not taken down and the crosshead has its regular
motion in the guides.
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THE, WALSCHAERT VALVE GEAR i8i
Q. 56.— In all of these cases of breakage it has been
assumed that we proceed, after doctoring up the
temporary disability, by using steam on the other
side of the engine but running with the main rod in
place on the disabled side, and the reasons for it have
been given; but suppose that the disability is the re-
sult of a broken main rod, and no other damage has
followed : What should be done?
A. — In case of a broken main rod on an engine
equipped with Walschaert valve gear, take down the
parts of the broken rod and disconnect the radius
rod as has been detailed before; if the valve is of
inside admission, push it to the forward end of the
steam chest and clamp the valve-stem or block the
slide to hold it in that position, or, if the valve is of
outside admission it should be drawn to the back end
of its travel and secured there, the intention in either
case being to keep the front admission port open for
steam to enter the cylinder and the back port open to
the exhaust. Then, with a bar, draw the crosshead
as far as it will go toward the back end of the guides —
until the piston is against the back head of the cylinder.
This is termed "steam blocking," and while steam is
being used the piston will stay placed, but in drifting
down hill, or receiving a jerk from the rear end of the
train at an application of the air brakes — bumps in
switching, etc., while steam is shut oflF, the piston
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i82 THE WALSCHAERT VALVE GEAR
is liable to get moved ahead and a sudden opening of
the throttle would send it back with force enough to
break the back cylinder head and ruin the guides;
so, after placing the valve and piston as directed, it is
best, also, to block the crosshead in that position.
There will, of course, be no movement of the combina-
tion lever, and it should not be disturbed; the only
motion of the valve gear on the disabled side will be
that the eccentric rod will continue to give the
regular motion to the link, but with the radius rod
disconnected from its suspension bar and the combi-
nation lever, and centred in the link, the action of the
link will have no effect.
Q. 57.— Suppose that the piston should get broken^
or detached from the piston rod in the cylinder : What
should be done in that case?
A. — Usually the result of this accident is to carry
away, or break, the front cylinder head; the head
should be removed, in either case, and the piston
taken from the cylinder. If the piston rod is not bent
leave the niain rod up and disconnect the radius rod
in the recommended manner, centre the valve, and go
on. The cylinder cocks, in this case, need not, of
course, be taken down as the cylinder is opened through
the removed head and piston.
Q. 58. — In connection with the preceding accident
suppose that the piston rod should be bent in the
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THE WALSCHAERT VALVE GEAR 183
cylinder : . Would you leave the main rod up in place
in that case?
A. — Certainly not. In addition to disconnecting
the radius rod and covering the ports by centering the
valve, as before stated, the main rod should always
be taken down — ^no matter how sUght the bend may be
in the piston rod.
Q. 59. — What should be done in case of simply
blowing out a front cylinder head?
A. — ^The radius rod should be disconnected in the
regular manner, the valve centred, and the back cyUn-
der cock, only, removed. About the only objectionable
feature in running with the main rod up on the disabled
side of an engine is not present in this case: It is
not an easy matter, usually, to keep the piston lubricated,
but with the cylinder head removed, oil can be intro-
duced as often as may be necessary.
Breakage, or blowing-out, of the back cyUnder
head is of rather infrequent occurrence, but when it
does happen, if the head is so slightly broken — say a
piece knocked out — that it will stand the pressure
of the piston under steam, the main rod can be taken
down (for undoubtedly the piston rod would cramp
in the stuffing-box if allowed to work) and the same
process followed as with a broken main rod, as pre-
viously described, steam-blocking the piston, etc., as
this saves time. In case the back head is completely
Digitized by LjOOQ IC
i84 THE WALSCHAERT VALVE GEAR
destroyed, however, the valve should be centred,
covering both steam ports, the main rod taken down,
and the radius rod disconnected and centred in the
usual manner.
Q. 60.— If the link bar connecting the lower end of
the combination lever with the crosshead should get
broken and lost, from both sides of the engine, how
could you measure for new ones?
A. — ^The length of these link bars could be closely
approximated as follows: Move the crosshead into a
central position that would indicate that the piston
was in the exact centre of the cylinder, and place the
reverse lever in the centre notch of the quadrant so
that the link-block pin and the link fulcrum pin, or
trunnion, are centred together; then move the lower
end of the combination lever until the lever is in an
exactly plumb, perpendicular position, and measure
from the pin hole in its lower end to the pin hole in the
crosshead arm to which the link bar should be con-
nected, this distance being the required length of the
link bar.
It is to be presumed that any one who is thrown into
association with the Walschaert valve gear is familiar
with the locomotive in general, and is already well-
informed as to the methods of procedure in cases of
breakdowns of the dififerent parts of the machinery
other than the valve gear, and for that reason no
Digitized by LjOOQIC
THE WALSCHAERT VALVE GEAR 185
troubles have been made the subjects of questions
except those that are peculiar to this style of gear,
or that must receive different treatment from that
which they would in connection with the Stephenson
Unk motion. There are many troubles that can, and
will, occur on the road that are not noted here, but
by understanding that which has been explained in
this book, any engineer that can keep the wheels
turning in the presence of the common disabilities
that occur to engines of the link-motion class, can
also be ready to meet any troubles that may possibly
happen to the Walschaert gear.
Digitized by LjOOQ IC
INDEX
Accessibility of Walschaert gear, 131, 132
Adaptability of Walschaert valve gear, 142, 143
Adjustment of Walschaert valve gear, 102
Advantages derived from the use of Walschaert gear, 129-148
Allan valve gear, and the Allen valve, 102
Analysis of the Walschaert gear, 11-92
B
Baldwin engine with Walschaert gear, 65 to 67 inclusive
Belgian engine with Walschaert valve motion, 80 to 87 inclusive
Bent piston rod in connection with preceding accident — should main
rod be left in place? 182, 183
"Blocking the valve" — what is meant, and how it is done, 171 to
174 inclusive
Breakage of lower section of combination lever, or its link to the
crosshead, 180
Break-downs on the road. Difiference in methods of disconnection
.of Walschaert and Stephenson gears, 170, 171
Broken radius-rod hanger, 178, 179
Broken valve-stem, 179, 180
Building up the Walschaert gear: The start, 28
Built-up Wabchaerit gear complete, 42
Case of broken or detached piston — what to do, 182
Checking dimensions of the gear, 98 to 100 inclusive
186
Digitized by LjOOQ IC
INDEX 187
Combination lever, 29
Comparative weights of Walschaert and Stephenson valve gears, 133
to 138 inclusive
Confusing in the meaning of lead, 158
Connections of the eccentric rod, 43
Constant lead with reverse lever in any notch, 38
Continuing the lay-out of the gear, and formulas, 105 to 109 inclusive
Correcting the built-up motion, 40, 41
Correction of one error introducing others, and their relief, 167
Could a broken side rod totally disable an engine with Stephenson
valve motion? In cases of break-down requiiing valve blocking
should valve-stem of the Walschaert gear be disconnected? 175
"Cut-off," meaning of, 160
De Glehn compound engine with Walschaert gear, 67 to 69 inclusive
Derivation of lead through the Walschaert combination lever, 157
Designing and erecting the Walschaert valve gear, 95-126
Designing the Walschaert gear, and explanation of diagrams, 104, 105
Details of the Walschaert link, 44 to 49 inclusive
Difference between Walschaert and Stephenson motions, 151, 152
Difference in set-up of Walschaert gear as between inside and out-
side admission valves, 62 to 64 inclusive
Different methods of erection, 49 to 51 inclusive
Different styles of set-up of the gear, 19
Directness of Walschaert motion, 138, 139
Direct valve motion, 20
Disconnection of radius rod. Method of doing it, 176, 177
X)isconnection of Walschaert and Stephenson gears, 170, 171
Does lost motion in the driving-boxes induce greater error in the
Walschaert gear than in the Stephenson motion? Does the ver-
tical motion of the engine affect the steam distribution in the
Stephenson gear? 164
Does the radius rod give motion to the valve, with reverse lever on
the centre? 160, 161
Digitized by LjOOQ IC
i88 INDEX
Does the rise and fall of the engine on springs affect the valve's
action with Walschaert gear? Position of valve with crosshead
in the centre of guides and reverse lever in centre notch of quad-
rant, 165
£
Eccentric rod broken. How to proceed, 179
Eccentric-rod connections, 43
Effect of broken side rod on engine with Walschaert gear, 174
Effects from lead, 154
Effects of valve advance to secure lead, 25
Engine standing as last mentioned, if valve is not exactly centred,
the cause and remedy, 166
Enumerating the chief advantages of Walschaert gear, 129 to 131
inclusive
Equalized cut-off, Walschaert vs. Stephenson gear, 161, 162
Erected gear, inspection of, loi
Erecting and designing the Walschaert valve gear, 95-126
Erection, different methods of, 49-51
Evolution of valve motion, 1 1
F
Formulas for Iky-out of the gear, 105-109
G
Gear, reversing, 37-39
General effects of lead, 143-148
General notes for adjusting Walschaert valve gear, iii to 113 in-
clusive
Heating of driving-boxes prevented by adoption of Walschaert gear,
141
Digitized by LjOOQ IC
INDEX i8o
Heaviest engine, and fastest engine, have Walschaert gear, 67 to 69
inclusive
Heaviest switching engine (decapod) with Walschaert gear, 75
Helmholtz modification of Walschaert 's gear; 113, 114
Heusinger Von Waldegg's modification of Walschaert gear, 92
"Hooking-up," meaning of, 160
How to get along with broken valve stem, 179, 180
How to proceed with Walschaert eccentric rod broken, 179
How Walschaert eccentric rod can be changed in length, 167, 168
If lead is not desired could the combination lever be dispensed with ?
Confusion in the meaning of lead, 158
Indirect valve motion, 26
Inside vs. outside admission valves, 16
Inspection of the erected gear, loi
Instructions for using cardboard valve models on the folder dia-
grams, 119 to 121 inclusive
Introducing cut-ofif, 33
Invention of Walschaert valve gear, 12
Is increase of lead desired? Does the established amount of lead
vary in the Walschaert gear? Advance of the valve for other
purposes besides securing lead. Is lead necessary ? 156
Kind of eccentrics used with Walschaert and Stephenson valve
gears. How the Walschaert motion is reversed, 152
Lap and lead; cut-off, 17, 18
Lap and lead with Walschaert gear, 30 to 32 inclusive
Location of suspension of the Walschaert link, and carriage of the
valve-stem slide, 169, 170
Location of suspension of Walschaert link, 76 to 80 inclusive
Digitized by LjOOQ IC
igo INDEX
Location of Walschaert eccentric in relation to crank-pin. Is the
Walschaert gear of direct or indirect motion ? Changed to either
by the shifting of the reverse lever, 159
Long's diagram of valve events, 109 to iii inclusive
L. S. & M. S. Ry. engine with Walschaert gear — heaviest passenger
engine, 73, 74
Mallet articulated compound engine, 62 to 64 inclusive
Mason's early design of Walschaert gear, 53 to 57 inclusive
Meaning of "cut-ofif" and **hooking-up,'* 160
Meaning of the term, "valve motion." From where the valve gear
receives its initial motion. Kind, or style, of valve used with
Walschaert gear. Difference between Walschaert and Stephen-
son motions, 151, 152
Meaning of "working quarter" of the crank-pin, 165, 166
Medal awarded Walschaert, 14
Method of disconnection, etc.^ with a broken main rod, 181, 182
Method of disconnection of radius rod, 176, 177
Motor car with Walschaert valve gear, 67
N
Nati\'ITY of Egide Walschaerts, the inventor, 13
O
Opportunity for rigid frame bracing in the use of Walschaert gear,
140
Outside vs. inside admission valves in connection with Walschaert
gear, 57 to 60 inclusive
Permanence of adjustment of the Walschaert gear, 139, 140
Permanency of adjustment of Walschaert eccentric. Wh n neces-
sary to correct its length, 168
Digitized by LjOOQ IC
INDEX 191
Permanency of the Walschaert gear, 52
Piston and D -slide valves, 17
Piston, broken, or detached, 182
Position of valve in relation to piston. What is meant by " lead," 153
Preliminary suggestions, 95 to 98 inclusive
Q
Questions and answers on Walschaert valve gear, 151-185
Radris rod, 35, 36
Radius rod suspension, 65
Reauleaux and Zeuner diagrams, 11 4-1 19
Reasons for Walschaert link curving in opposite direction to the
curve of the Stephenson link. Impossibility of changing the ad-
justment, or experimenting, with the Walschaert gear, 162
Relation of eccentrics to crank-pin, 21 to 25 inclusive
Relative positions of reverse lever and radius rod, 161
Reversing gear, 37-39
Securing lead, 27
Securing lead with Stephenson eccentrics. Securing lead with Wal-
schaert motion. Does the amount of lead remain constant in
the Stephenson motion? 155
Set-up of the gear — different styles, 19
Simple comparative test of Walschaert and Stephenson valve gears,
148
Suggestions as to certain dimensions and proportions of the Wal-
schaert gear, 103
Test of Walschaert and Stephenson valve gears, 148
The Allan valve gear, and the Allen valve, 102
Digitized by LjOOQIC
XQa INDEX
The built-up Walschaert gear complete, 42
The combination lever, 29
The general effects of lead, 143 to 148 inclusive
The radius rod, 35, 36
The Reauleaux and Zeuner diagrams, 114 to 119 inclusive
The reversing gear, 37 to 39 inclusive
The several efifects from lead. Use of a compression instead of
lead, 154
The valve, 15
The Walschaert link, 34
Theory of the combinaton lever, 96, 97
Use of Walschaert gear indicated on engines with crank-axles, 141,
142
V
Valve gears of De Glehn compound, 69 to 73 inclusive
Valve models, instruction for using, 11 9-1 21
Valve motion, indirect, 26
Valve the, 15
Variations in the angle between eccentric and crank-pin, 121 to 126
inclusive
W
Walschaert eccentric rod changed in length, 167, 168
Walschaert eccentric rod may be changed in length. Other parts
of the gear. Does any particular part of the Walschaert gear
have a tendency toward heating? 163
Walschaert gear adjustment, 102
Walschaert gear, Helmholtz modification of, 113, 114
Walschaert gear, ^^ason's early design, 53-57
Walschaert gear unaffected by side-rod breakage, 84
Walschaert gear with piston valves, 60 to 62 inclusive
Digitized by LjOOQIC
INDEX 193
Walschaert link, 34
Walschaert link, details of, 44-49
Walschaert motion, reversed, 152
Walschaert's original design of valve gear, 87 to 92 inclusive
Walschaert* s patent, 14
What is meant by "lead," 153-
What parts of the Walschaert gear should be kept especially free
from lost motion? 163, 164
What to do in case of blown-out front cylinder head, 183, 184
What to do in the case of broken radius rod, 178
Where links between crosshead and combination lever are broken
and lost from both sides of engine, how to determine the correct
length for new ones, 184
"Working quarter" of the crank-pin, meaning of, 165, 166
Zeuner and Reauleaux diagrams, 114-119
Digitized by LjOOQ IC
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the manufacture of genuine and useful electrical appliances. Fif-
teenth edition. Fully illustrated. 183 pages. Cloth. $1.00.
SLOANE:. Liquid Air and the Liquefaction of Gaaea.
Containing the full theory of the subject and giving the
entire history of liquefaction of gases from the earliest times to
the present. 365 pages, with many illustrations. Second edition.
$2.50.
SLOANB. Standard ESlectrlcal Dictionary.
A practical handbook of reference, containing definitions of
about 5,000 distinct words, terms and phrases. An entirely new
edition, brought up to date and greatly enlarged. Complete, con-
cise, convenient. 682 pages. 393 illustrations. $3.00.
VSHKR. The Modem Machinist.
A practical treatise embracing the most approved methods of
modern machine-shop practice, an.d the applications of recent
improved appliances, tools and devices for facilitating, duplicat-
ing and expediting the construction of machines and their parts.
A new book from cover to cover. Fifth edition. 257 engravings.
322 pages. Cloth. $2.50.
VAN DKRVOORT. American Lathe Practice.
A new book from cover to cover. It is strictly up-to-date In
its descriptions and illustrations, which represent the very latest
practice in lathe and boring-mill operations as well as the con-
struction of and latest developments in the manufacture of these
important classes of machine tools. A large amount of space is
devoted to the turret lathe, its modifications and importance as a
manufacturing tool. 320 pages. 200 illustrations. $2.00.
VAN DERVOORT. Modem Machine Shop Tools; Their Construc-
tion, Op'^ratlon and Manipulation.
This is a book of reference that will be found convenient
In every machine shop. Suppose it is desired to know how to
cut bevel gears, to calculate milling machine spirals or to make
countershaft calculations; or to get Information about tap drill
sizes, the classification of files; change gear calculations; deep
hole drilling; turning tapers; testing lathes, etc.; or any one
of the numerous questions that a little information might be de-
sired upon occasionally — these pages will be found to contain
the satisfactory answer. The book will also prove a boon to
students in manual training, as by studying its pages and apply-
ing its principles to the school shop, they will be able to acquire
a good knowledge of shop practice. The book has numerous
tables, and In addition to the chapters strictly on tools are
several on fastenings, gearing, belting, shafting, and the treat-
ment of steel. 552 pages and 673 illustrations. $4.00.
IVALLIS - TAYT^OR. Pocket Book of Refrigeration and Ice
Making.
This explains the properties and refrigerating effect of the
different fluids in use, the management of refrigerating machinery
and the construction and insulation of cold rooms with their re-
quired pipe surface for different degrees of cold; freezing mix-
tures and non-freezing brines, temperatures of cold rooms for all
kinds of provisions, cold storage charges for all classes of goods,
ice making and storage of ice, data and memoranda for constant
Digitized by LjOOQ IC
Publicationg of The Norman W. Henley Publishing Co,
reference by refrigreratingr engrineers, with nearly one hundred
tables containins: valuable references to every fact and condition
required In the installment and operation of a refrigerating
plant. Price. S1.50.
WOODWORTH. American Tool Blaklnv and niterchanveable
Mannfaetnrinv.
A complete treatise on the Art of American Tool Making and
System of Interchangeable Manufacturing as carried on to-day in
the United States. In it are described and illustrated all of the
different types and classes of small tools, fixtures, devices and
special appliances which are in general use in all machine manu-
facturing and metal working establishments where economy, ca-
pacity and interchangeability in the production of machined
metal parts are imperative. 500 pages. 600 illustrations. Price,
14.00.
WOODl^ORTH. Dlea, Their CcMiatractlon and Vue for the Modem
Worklnv of Sheet Metals.
A practical work on the designing, constructing and use of
tools, fixtures and devices, together with the manner in which
they should be used in the power press for the cheap and rapid
production of sheet metal parts and articles. Comprising funda-
mental designs and practical points by which sheet metal parts
may be produced at the minimum of cost to the maximum of out-
put, together with special reference to the hardening and tem-
pering of press tools and to the classes of work which may be
produced to the best advantage by the use of dies in the power
press. Fourth edition. 400 pages. 500 illustrations. |3.00.
WOODl^ORTH. HardenlnsTy Temperlnflr> Anneallnflr and Forfflns
of Steel.
A new book containing special directions for the successful
hardening and tempering of all steel tools. Milling cutters, taps,
thread dies, reamers, both solid and shell, hollow mills, punches
and dies, and all kinds of sheet-metal working tools, shear
blades, saws, fine cutlery, and metal-cutting tools of all descrip-
tions, as well as for all implements of steel, both large and small,
the simplest and most satisfactory hardening and tempering pro-
cesses are presented. The uses to which the leading brands of
steel may be adapted are concisely presented, and their treatment
for working under different conditions explained, as are also the
special methods for the hard<ening and tempering of special
brands. 320 pages. 250 illustrations. $2.50.
AVRIGHT. CSlectric Fnmacea and Their Industrial Applications.
Contains 285 pages, and 57 illustrations, which are essentially
In the nature of sectional diagrams, representing principles of
construction. This is a timely and practical treatise on the forms
and uses of electric furnaces in modern electro-chemical pro-
cesses. Price, $3.00.
>^ or THE
UNIVERSITY
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UNIVEBSITY OP CALIFORNIA LEBEARYp
BEEEELET
I
THIS BOOK IS DUE ON THE LAST DATE
STAMPED EEIiOW
Booke not returned i>n titae ArA anfajeet to & fine of
60c per Tolume after the third d&y overdue, tneTeaiing
to 11.00 per Tolume nftfir tha glxtfa. d»f. Booki not in
demand may be Ten e wed if application is made bafor*
expiration of loaii period.
^
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AN S6 Y^k
7
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1930
OCT 7
50m-7,'37
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